I have to admit that part of the incentive for me to think about quitting last decade was after i made my first million.... I was thinking damn, life is good, people are good and here I am killing myself. What's the fucking point? GROW THE FUCK UP.
If youve got hopes and ambitions you have to think that way. But then....... you know, when you realise that each one has like 2000 chemicals (the effects of which from some of them are unknown) it brings it home. Actually that site i gave above has a lot of factual info, make sure you read it:
http://whyquit.com/joel/Joel_02_17_smoke_in_lung.html