First get a journal. Write down everytime you use this behavior. Think about the situation that brought it on and think of an alternate or more positive behavior to replace it with. Once you recognize when and why you use the behavior, try to catch yourself before you do it and replace it with the positive one. Shoot for doing this once a week at first and increase over time. I will not lie, it takes a long time to change, but it can be done. Don't be affraid to include friends and/or family in the process. A little help goes a long way. Good luck.