Powerful answer to the question "Why haven't I committed suicide yet?" It was written by a astrophysics professor at the University of Illinois who also suffers from bipolar disorder. It struck me as the best written reason I've read for why I haven't gone and offed myself:
"What I finally came up with is that my life isn't really "mine". It belongs to me, sure, but in the context of all the other lives it touches. And that when all the chips are down on the table, I don't have the moral/ethical right to destroy my life because of the impact that would have on all the people who know and love me.
"Killing myself implies killing part of them. I could understand very clearly that I did not want any of the people I love killing themselves. By reciprocity, I realized that they would say the same of me. And, at that moment, I decided I had to hang on as long as I absolutely could. Today, needless to say, I am very glad I made that decision."
(found at: http://www.healthyplace.com/Communities/Bipolar/Mihalas/bipolar_disorder_depression_7b.htm
Bunch of interesting tests here, including a depression and personality disorders test: