If you try to kill yourself and fail, that means it was a half-hearted effort, and part of you wants to go on living. I have a cousin who attempted suicide, sweet as can be, but when she talks about the feelings going through her mind when she tried to kill herself, it gets really dark, at the same time, she admits that she probably could have taken it a step further and guaranteed death, but she didn't, and doesn't really know why, but is happy that she didn't kill herself said day.
Rule of self-preservation keeps most people from doing anything to endanger their lives, at the same time fear, love, pain can all cause you to ignore it that golden rule. >_>