I've been a happy smoker for the better part of fifteen years, starting at 13, rolling my own since 15 and never really thinking of quitting as I lived on black coffee and cigarettes in a local jazz bar all through high school and college (this was when you could still smoke in bars). It didn't even bother me that much that I was sick for weeks on end every winter and couldn't ride my bike for a mile without needing to lie down. I once had a cough so bad an on-call doctor thought I might have tuberculosis. I read the Allen Carr book that month, and managed to quit for a whopping 8 hours.
It wasn't until I hit 30 and got serious about quitting, that I got stuck in the horrible Sisyphean cycle of addiction. It looks like this: