I smoked for 9 years. (I'm 25 and quit 2 years ago).
Early on you must think about it like you're building upon days of being a non-smoker. And accept the fact that you will never smoke again for the rest of your life, or you will sabotage yourself.
You'll never regret it. Looking back, probably one of the most retarded things I ever took up.
2013 535i xdrive(Current)
2008 E92 M3 (Gone)
2006 E90 325i (Gone)
2002 E46 325xi (Gone)
1991 E30 325i (Gone)