I'll just quote an older comment of mine:
«Je ne vis que parce qu'il est en mon pouvoir de mourir quand bon me semblera: sans l'idée du suicide, je me serais tué depuis toujours.»
- Cioran, Syllogismes de l'amertume
(I live only because it is in my power to die when I please: without the idea of suicide, I'd have killed myself right away.)
I used to think like this as well, and still try to some extent, until I chanced upon several first hand accounts from users of this website who were grimly determined to follow through with their plans of suicide, only for their attempts to be thwarted by that seemingly all-powerful survival instinct.
It is not dissimilar to the case of a man who calms himself with the certainty that he has enough money in the bank to get through difficult times, only to discover at the crucial moment that his bank account is empty.
I try to take comfort in the thought that I always have the option to "die when I please", but with each passing day, I cannot help but feel more and more like a gambler who tells himself that he could always win back what he lost if he only tried, despite knowing full well that it is not true.
The thought of suicide used to calm me down, but the more I dwell on it, the more it does the opposite: I reach for the emergency brake, but there isn't one there.