Living a healthy lifestyle can be hard work, the real true key is controlling the mind. Reprogramming the sofware inside your head that gives you cravings and tries to get you to do the things in life you know aren't helping at all. Until you can have full control over the things you do without giving in to your emotions you'll never beat it.
Most of my clients who succeed are the ones that manage to think of food as fuel, which is essentially what it is. My advice is to start reading all you can about mind reprogramming techniques. I really like any of Paul McKennas stuff but there are plenty others out there to choose from.
Jago