Katie, this is perfect. I've been successful with avoiding my DOCs but I've always needed something else-- school, work, whatever-- to focus on. Constantly telling myself I can't do drugs or drink just reminds me that I wouldn't mind getting drunk and high. Eating right, exercise, and having a balance of intellectual pursuits and fun is much better than sitting in my house saying, "I can't do drugs. I don't want drugs. I won't do drugs."
It's like the old, "Don't think of an elephant" thing. You immediately think of an elephant. And of course... my elephant resides in the living room, right?