I quit once for 2 years, but a relationship going haywire started me back up on smoking, just like how I crave a few beers after a long day.  I remember days when I would just spend nights trying to stop myself from driving to the gas station to buy one more box of Camels.  I would go clean for a few days and I'd think "One cig won't kill me."  Before I know it I'm back to smoking 2 packs a day.  One thing I know -- if you're an obsessive / compulsive, it's impossible to just be an "occassional" smoker.
How did I quit?  8 years ago, I gambled / played tourneys in pool halls 24/7 all over my state.  If you spent time in pool halls, you know everyone is stoned in there and you're usually surrounded by lots of smoke.   One day, I picked up the habit of chewing gum instead of smoking and after 1 year, I realized I wasn't smoking anymore.  It took no thinking, no will power, no counseling -- just packs and packs of gum 
