I don't think this is philosophical but here goes nothing.
Firstly, I'm assuming that, after death, there is non existence and no afterlife. In other words, we do not have the sentience to comprehend or visualise or interact with anything. It's completely dark but you don't know that as there is no "you" anymore
Now then, when I consider my reasons for suicide, I look at how death would actually impact me relative to me existing right now. If I died right now, my suffering would end and, relative to my current state, I'd be more at peace even if I can't comprehend said peace.
Additionally, and this is really important, for those who say that I get a better chance of a better life if I continue living, I say that, if I do kill myself right now, there would be no future for me as I do not exist and even if I were to hypothetically get better were I to continue on living, it wouldn't matter to me as I'd be dead and hence I can't feel regret or any feeling. Sure, I may miss out on happiness if I'm dead but, simultaneously, I'd also not be able to comprehend that so I can't really feel depressed over this if I'm dead.
In other words, it doesn't matter if my life were to get better in the future or not; I should kill myself now to prevent further suffering