This is going to sound very cheesy, but you need to love yourself.
When you truly love yourself, you are good to yourself. You are good to your body, you nourish yourself with good things, and overall your health improves. Self-destruction (bad eating habits, drugs, alcohol, partying etc) are all because we are either escaping from something we have trouble coping with, or because we feel that we aren't worthy of something better.
I would say loving yourself (inner healing and betterment all included in that) is the first step to true health :)