I think the best motivation is early success. When I first started paleo two years ago I lost 11 pounds in a week just by removing grains and junk from my diet. That led me to remove other horrible things from my diet like fruit juices and to start exercising. After 5 months I'd lost 40 pounds and have kept it off ever since. Since then it's just become my lifestyle and no real motivation is necessary.
We are creatures of habit, and some discipline, after the goal has been reached.
![thup :thup: :thup:](/styles/smilies/thup.gif)