I've never smoked, so I don't know how hard it is to quit, but I have experience helping people quit. One thing I've thought of is to change who you are. Think of yourself as a non smoker, not as a smoker that's trying to quit.
Imagine you go to a gas station and see the cigarettes there. You may think. "I'm a smoker, but I'm trying to quit so maybe not this time, but they look so good. Maybe just one. I'll just try to make this pack last longer than the last one."
Instead, you need to think. "I'm a non smoker. Those cigarettes don't even tempt me at all." Or If your friend offers you a cigarette, just say "No thanks, I'm a non smoker" or "No thanks, I don't smoke."
Here's a list of things that might help
• Acknowledging that the behavior is harmful. It affects others and requires change.
• Being humble and feeling sorrow.
• Seeking forgiveness from others who have been harmed, and learning to forgive one’s self.
• Stopping addictive actions and beginning to do healthy things.
• If you mess up, don't beat yourself up. A lot of people relapse. Always be willing to try again.
• outline the times, places, and people that contribute to the behavior. Then discuss the list with a trusted friend. Talk about what they need to do to change or avoid the items on the list.
•write down what the behavior is causing them to miss now and, if not corrected, what it will cause them to miss in the future.
•write down different things they can do to avoid or discourage inappropriate behavior. This may include talking to your spouse, calling a friend for support, exercising, and any other activity that helps them avoid temptation.
You could also try prayer with this. It never hurts to have God's help.