Not sure if it's a wives-tale, but my Grandma told me if I keep cracking my knuckles I'll get arthritis, and my knuckles will become enlarged. I stopped. That probably won't work, since you already know you want to stop.
When I need to remember something, I put a rubber band or pony tail holder on my finger. It's really annoying, and keeps reminding me of what I have to do.