just replace the habit, i recently read a book on this actually.
so there are three steps in a habit - the trigger, the action, and the reward. all three are driven by a craving. you crave the cigarette, the trigger might be stress, or simply thinking about smoking, as a result of the trigger, you then light up a cig (this is the action) and as a reward, you get the head buzz.
you can't kill habits, but you can change them. the way to do this is to change the action. so from now on, whenever you feel your trigger (whatever it may be) you need to do something other than smoking. you could go lift, or you could snap a rubber band on your wrist... you could literally do anything at all, just STAY TRUE TO IT. the best replacement actions will reward you with a similar rush, so i'd say exercise would be a good one. eventually your habit will be changed, and you'll instinctively go to work out when you crave a cig... you won't have to force yourself to. and at this point, your craving for nicotine will be gone.
good luck man. you can do it.
