"Slips" happen when you have a cigarette while you are trying to reduce or quit. It is a good idea to be ready for slips. Do not let the slip lead to returning to smoking. Make a plan to prevent slips and to deal with them if they happen.
You can prevent slips by using the same tips for dealing with cravings. Think about what situation you would most likely be in if you were to smoke again, and then think about what you would do so you don't smoke. It might help to write these ideas down.
You can also watch for warning signs such as thoughts or actions that usually happen before a slip.