If you consider that all existences live and is manifest simultaneously in terms of space (everyone in physical reality that you know, exists at this exact same moment in time that you are in, and they appear as separate physical entities in space, along with the environment), and space is directly related to the concept of time, then it's not difficult to think of time as being simultaneous as well. The difficulty in imagining this is because of the perception of a beginning and an end from within a single point in space (your body). It is because your frame of reference is from a single point in space that you cannot see the simultaneousness of time. Your frame of reference within time is also from a single point in space/time at any given moment.
You cannot see what someone on the other side of your planet is doing at this very moment, nor could you know if someone exists on another planet in another galaxy or what they are doing at this same moment. In the same way, you cannot know from this point in time what the experience of the moment will be in a future time because it is like the space that is hidden from your perception. Time is hidden from your perception as well. You could imagine a future, just as you could imagine a location, but you are not physically experiencing that moment in the future or the location in space. The past is like the memory of a location you had visited before. You remember the physical qualities of the space you were at. In the same way, your memory of the past is just like your memory of a previously visited location. You are not at that location, nor are you at that moment in time. You may revisit the location, but it will not be the exact same state of that location as it was when you first visited. In the same way, you cannot revisit the same moment in time. It will always be a new moment in time. In this way, you are always creating a new space and a new time.
If you understand how space in physical reality is divided into 3 dimensions of directionality, then time can be thought of as all of 3D space contained within a moment of time (don't think of 3D as being actually existing as matter and this idea becomes easier to accept). This contained space exists for every moment of time and that is the dimension that carries you forward through the infinite moments of space. Just like moving from point A to point B in space changes your perspective of the space around you, so too does the moving from time A to time B change your perspective of everything around you. The main difference between space and time is that you do not have to change your position in space because you are in the space bubble of "now" (this does not mean there isn't change in space since you must breath and your heart beats). But time is always moving forward so your experience of space in the "now" will always be changing as well, as you "jump" from one "all space" in a given "now" moment to another "all space" in a new "now" moment. You are carried along the river of time with no control while experiencing physical existence in a bubble of time at every "now" moment.
If space and time are simultaneous, then you are connected to everything through that simultaneousness. Not only are you connected, but you the creator as well, through these connections. You may not see these connections to everything around you while viewing your life through the 3D point of view, but that connection is what allows you to have a 3D experience at all (try not to imagine "connections" like strings tethering you together. It is an analogy. The connections exist because you are all of the perceived things, not that these things are separate with actual connections with you). The "experiment setup", the conditions for life, the time period you are born into, the culture you are raised in. These all shape the experience you will have in the new life created as "you". While "you" are an eternal being made of the "God" stuff (spirit), you are a new creation (soul) born into this portion of space and time (body). Unlike religious concepts of body, soul and spirit, there is no true separation of these three concepts. They are merely 3 different words using language to represent the portions of "you" that gives you different perspectives.
From the body perspective, you have those "instincts" and behaviors meant to enable "survival" (to stay in physical form and have the experience rather than returning back to the All-ness). The body is from the same source of mind as you (spirit), but acting as the bridge/interface between the "you" as All That Is creating the physical reality, and "you" as the personality experiencing life in physical reality. From the soul perspective, you have an identity and a sense of individuality to make decisions and define your perspective. Your "life" is recorded as your "soul". From the spirit perspective, you are the life that allows for experience and existence, the first body and soul being a manifested portion of the spirit. The body (waking consciousness) is the spirit, creating together with all of the other "bodies" (any physical matter), the "objective" reality. This can be called the "shared subjectivity". The soul (the sub-conscious) is the "non-physical" spirit creating together with all the other "souls" that you are (multiple lives) the "individual subjective" reality through a "physical" body, an identity. The spirit (the unconscious) is the living energy (Logos) that always exists and is the foundation for all existence.
You as a soul within space and time is not something that is left alone and without any knowledge. The spirit creates a soul as the cumulative bundle of other souls. It is not multiple souls being "put into" another soul, which is a spatial concept (and religious concepts such as karma and reincarnation). Rather, certain qualities of each soul's experience/perspective is brought together in certain proportions and this combination of qualities creates a new combination within a soul that creates the backdrop of a new personality. A soul does not "return" to live another life, unlike the ideas of reincarnation. When you think of someone's behavior or characteristic, this backdrop of qualities that come with the new born soul is why you have personality. If one were to come into existence without these qualities, they would feel lost and confused in the time period they are born into because the rest of the living have already been "trained" into that social norm. But most new individual perspectives do have a set of qualities that give them a "head start" within physical life to grow into a new identity. That is why you were given free will, to choose in life what you want to be.
Being born with a set of qualities does not mean you are born with just qualities. You are born with these connections to your other souls within you (which is why you have those qualities; there is no separation), and those connections are strong or weak depending on which connections you strengthen or weaken through choices. You resonate with some and not others through your choosing. This resonance with certain qualities comes through in your current life and at the end, a new unique combination of qualities will have been made within your soul. You then are also a source of qualities for another soul. Your mind is the communication through these other soul connections. This is where your thoughts, inspirations, ideas, worries, feelings, etc. can come from. But you as the central soul in this body coordinate those thoughts that you experience as your own to make choices.
In a simultaneous space/time reality, those connections with your other selves are also simultaneous. Those other souls are also living their own lives while you live your life simultaneously. This implies that new space/time is always being created as well. But that is obvious once you realize that space/time is the creation of spirit, which brings into existence you as a new soul. The new soul is a part of the creation of the space/time. So from spirit, the cycle of life/space/time exists within simultaneous existence. Not only are you creating yourself, but by creating yourself, you create space/time, and the connections with the other simultaneous space/time alters their reality just as their changes alter yours (how else could it be if they are your thoughts that you act upon, just as you are their thoughts). All of existence is change, and as you grow and change, your experienced space/time changes, as well as the connections to your soul "minds" also change their space/time, which then changes the connections within their soul minds (all souls are creations of bundled soul qualities). If you can understand this idea, then it may become clear that there is no beginning and no end, since all is happening "now" and are are interconnected and all are One.
As explained, the one thing that is not bound by space and time is your mind. You can feel the same whether you are 10 or 100. It is only your understanding of your reality that differs with time. That happens because of change. The only thing that truly exists is you and change. Your physical appearance changes with the expectations of change within the rules of the physical reality. But within the physical reality, you remain "you". Time only affects the amount of experience and hopefully, conscious awareness. The point of experience is to increase your awareness of yourself. If you want to believe in a purpose for 3D life, you could say that you are experimenting. You have put yourself in this space and time to find out how you would react in the circumstance you end up in. Can you, as an eternal being of "love", remember that you are an eternal being of "love" while experiencing not being "love" or will you succumb to your environment? This is what it means to be your true self. The true self within is "love".
The word "love" is not the emotional definition of love. It is the creator definition of "love", which is acceptance of all creation. Why is "love" not the emotional definition? Because that definition only requires to you feel something fleeting towards something else. Acceptance requires you to allow the something into your heart. You can feel an emotion without accepting them because that is an intellectual thing, even if you do not realize this. Acceptance is the act of allowing its existence.
You are Existence outside of the 3D perspective, and so is everything else. Therefore, you automatically accept everything since it is all you. But in 3D, especially in 3rd dimensional experience, you are born forgetting this fact in order to experience your creation as it is. Creation is not about the emotions. Creation is about your creativity of creating. It is expressing all the infinite ways of "being". If everything is an expression of "being", including that which might be considered "bad", can you still accept it as a part of you? If you cannot, then you will continue to experience all of your own creations until you can accept them as "you". This also asks if you can accept yourself as you are, to "know yourself"? If not, then become who you wish to be.
This is why you created space and time as a 3D physical existence. Space provides a way to experience each of your creations as if it was separate from you so that you can love it. Time provides a way to make choices and experience the consequences of your choices in order to define yourself within the new creation that you are. Without the benefit of time, you could not gain the understanding of what a choice means if there was no consequence. If you could re-live a moment with a different choice, then the experience would not be impactful (produce change). Granted, outside of physical reality, you can re-live moments, you can experience all possible choices and the consequences, but it is more academic in experience, rather than something like a surprise or a gift or a spark of inspiration (it would be like cheating, with no true benefit).
That is the beauty of space/time that you live in while alive in 3D. I hope this understanding helps you to appreciate all of life's experiences, both that which is "good" and "bad". Do not judge a moment in a negative light without trusting that you created it for a purpose. Do not look at your surroundings as if you are separate from it because you will lose your perspective of space and time by focusing on the point in space and time that you believe you are in. Rather, remember the expanse of space and time that exists simultaneously and that you are a part of its creation, along with everyone and everything else that make up your experience of 3D life. You do not have to lie and say something is enjoyable if it is not. But remember that there is a bigger picture and a bigger purpose than the goals or ideals only within physical reality. The things that seem important or beneficial or desirable within physical reality is only those things if you believe that they are all that's important to you.