I personally don't think it is bad (wrong, sinful) to 'top' oneself, though I would prefer the people I leave behind not to have to clear up my mess (actual emotional plus other messes no doubt).
I would often consider it a waste..... I think (hope) most people do have a contribution to make to family, society, art, sport etc.
But to get an answer to your question you would probably have to go to a theist to find out "
why it's so bad to kill yourself?"
This likely is a subset of Danarch's thread:
http://www.agnosticforums.com/philos...ght-wrong.html
I don't particulary believe in "right and wrong" when it comes to morality, "wise and unwise" seems a better concept though this is not perfect.
all the best