I found a great post at lifehack.org that details some methods on How To Stay Motivated. Gleb, the author, takes you through 5 steps:

1. Find the good reasons
2. Make it fun
3. Take a different approach
4. Recognize your progress
5. Reward yourself

This is a great way to get yourself focused on what you want to achieve - not only with your health - but in your life. If you don’t have clear and specific health goals, now is a great time to come up with some.

Then, using Gleb’s methods, keep yourself motivated and working towards achieving what you want. I particularly like his section on making things fun. If something is a drag, I don’t want to do it - even if I know it will get me closer to my goals. But if I think about it long enough and with a good attitude, I can usually come up with something fun or positive to focus on. After a while, the positive attitude becomes a habit.

You can read the entire lifehack.org post here: http://www.lifehack.org/articles/productivity/how-to-stay-motivated.html