Living forever in the past is not even possible. That way I would be infinite years old. And everyone knows that you can't ever finish infinite years, there's always more, so there would be no possible way to arrive in the present. On the other hand, living infinitely into the future is possible (not considering the heat death of the universe).
That is a massive misunderstanding of the involved mathematics, in both these cases.
In the first case, it is inevitable to "arrive in the present". Every single moment along this infinite line of time IS the present.
But here, this is not the problem. Consider: if you exist - and especially if you exist in a situation where you once didn't exist - there is always the possibility of non-existence.
If you - irrationally - fear non-existence, and exist eternally...
you will never ever stop fearing to not-exist.
There is infinite time and my lifetime (likely around 80 years) is 0% of it. Even if my life is very important, it's value can be calculated by multiplying it's importance with that zero. It always gives 0. Life must be eternal to have value.
Using a wrong frame of reference for that. The value of something is limited to this something, is not a fixed value, and isn't streched out to cover instances beyond this something.
If you followed the mathematical reasoning of your example, it would mean that in an eternal life, no single event could ever have any value... because any possible value
divided by infinity is also 0.
Congratulations, you now have eternal life, and this eternal life has "value". But nothing IN your eternal life has any value.
It simply doesn't work that way.
Fear of death may be useless, on a higher level (it does protect me from dying to some degree). However it's not irrational. That my life could be limited is something to fear, but that fear doesn't just help me at all.
You keep repeating that it is something to be feared... but you never bother to explain the reason.
And you also shift your targets. That your life is limited is indeed something to be feared. Death is something to be feared. It is real, it will happen, and it will harm you. You have to deal with this fact and with this fear.
But you started with saying that "not experiencing anything" is the thing you fear... and that is irrational... because it is absolutely, totally, completely 100% IMPOSSIBLE.
It is not only something that is unlikely to happen to you, or, if it does happen to you won't harm you in any way. It is something that just is not real.
I must add that before I was born, there was still hope. I was to be born in the future.
And it didn't elevate or bother "you" in any way... because there was no "you" to hope or fear. It will be the same after you die.
Same with sleeping, anesthesia and 1000 year cryopreservation, nothing to worry about. I will wake from it. Death, according to you, is permanent.
If I popped back into existence for a day every million years, it wouldn't be scary.
I will readily admit that I am no psychatrist or psychologist or any other kind of mind-tinkerer. I do not really understand what motivates you here.
If you came here and told us that you feared open places, I wouldn't know how to deal with that. The fear of open places is irrational, but open places do exist, you can experience them, and this might cause you fear.
I could tell you that open places are nothing to fear... but you just do. It is nothing rational. I understand that... I just don't know how to solve this.
But you are also here to defend your fear. You adamantly insist that open places MUST be feared. That people who do not fear open places are suffering from "mental disorder". And that you only do not succumb to your fear because you KNOW that all open places will be roofed over and narrowly walled in.
It seems to me that you don't want to remove your fear... you just use it as a cherished tool to defend your personal view of a solution.