i read these five tips on how to break a bad habit and found them pretty motivating and true in cases where i've been able to break them.
here's a brief list - but i highly suggest you read the full version on the blog:
1. get a running start
2. try to change your habits during a busy time
3. no exceptions - do not give in to temptation on any relapses
4. head off temptation
5. consider marshmallows
via the happiness project