I don't think I would have trouble with existing if I were to lead insignificant/purposeless/meaningless but enjoyable life. I thought that maybe I'm not behaving fully reasonable because I'm still alive, but actually i don't know whether I would be better off dead because I have nothing to compare. It's like choosing the bigger one between defined and undefined values. I do believe that the closest thing to death in terms of enjoyability is something that doesn't have any good or bad feelings -- of zero value...
I have no idea why do I care about enjoyability of life, or why would I consider life to be unworthwhile compared to unlife in the first place, or why do I want to avoid unenjoyable/undesirable/unsatisfactory/painful things. Kinda funny, aren't pain-pleasure and emotional (same purpose but more complex, I guess?) systems are supposed to keep me (us) alive? Because some of us believe/think that dead don't experience pain and emotions can as well drive to suicide. But survival instinct supposed to take care of it anyway, right?
But maybe it's not the only stopping factor; something also prevents from even trying, but it doesn't stop me when I'm emotionally driven enough. I can't think of any similar situation other than confronting bad habits, so it may be them, instincts and habits. Like hard and soft programming, perhaps?
Some say that it is hard to execute even (presumably) painless/easy/secure methods (like n, sn, some artery suspension, or what not) because SI still gets triggered. Whatever it is, it may read the rational brain output, and kick in when any meaningful danger to life is perceived, so you can't trust rational brain in that sense, but you have to, if you hope for predictable and desired outcome... I don't know what kind of trick we can pull off... Use the brain to organize the plan --> somehow turn the rational brain off partially (enough not to perceive life threat, but not enough to follow the plan?) --> follow through the plan? Or wait for the terror of flames to occur spontaneously? Something in-between?
Good thing (I hope) that our brains are going to decay eventually, to the point of losing some of undesired functions/functions presumably responsible for distress with living. (Think and interpret stuff. I assumed that's what you meant by the end of life.)
We are here because we are well-constructed/skillful/fortunate at living and preserving, I guess. Those who weren't as good at living aren't living. I don't know why is that; maybe some of us are barely good, somewhere on the borders of living realm, marginals. (Ha, ha.)