First off, I want you to know, the reasons vary with person... I was suicidal 3 years ago, and I still have those dark looming thoughts...
These are the reasons I used to not kill myself back then:
If I die, I can't paint.
If I die, I can't support my friends.
If I die, who is going to be a good influence to my little brothers.
If I die, I'll never be able to know what it feels like to be loved and wanted.
If I die, I'll lose the chance to meet my soulmate.
If I die, I won't be able to be an author.
If I die, I may lose the chance to know what it's like to live without being depressed.
If I die, I won't be able to pick flowers.
I basically took all the things I loved doing, and used them as a reason to continue living...
But I also did this:
If I kill myself and someone out there actually loves me, they'll be heartbroken.
I hate being the cause of anyone's pain, and commiting suicide would be the cause their pain...
But... If none of that works,...
How about, you'll never get the chance to see the change you're wanting to see if you kill yourself, because then it's one more person who is out of the fight. And that's one less voice fighting for that change.
The thing is, we never truly want to die... We want to escape the pain we're in, the pain we feel... And the only way we know would work, is to commit suicide... But what we don't realize is commiting suicide doesn't kill our pain... It gives it to someone else....
There's an Arabic Proverb that goes something like: You say you want to die. Throw yourself out to the sea and see yourself fighting to survive. You don't want to die, you want to kill what's inside of you.