Why do people kill themselves?

I think they do it when they can no longer find a reason to keep going. When nothing in heir lives is good enough to balance out the bad. And they do it when they no longer have the courage to carry on past some recent painful experience. They commit what is, in the end, a desperate, final call for help, that is hopefully heard in time by someone else.

And what if it's not heard in time? I ask although I know the answer.

Then they die.