from the internet : Nicotine addiction is not the main problem in stopping smoking. Your system usually gets rid of the nicotine with in a week , so why is it that people can give up smoking for few months and then take it up again? The reason is simply that they have never overcome the Psychological habit of being a smoker. The habit is lodged in the subconscious mind so that there is a constant desire for a cigarette. It is the nagging desire that this habit creates which will gradually wear the you down, until in a moment of stress or weakness they give in and light that first cigarette. You can’t quit unless you hit rock bottom.