You’ve gotten excellent suggestions so far. I would echo some, and add a few of my own; these things worked particularly well for me.
Visualization. Picture where you want to be. I hate to run, but it works for me like few other things. So every step, I’m imagining the body I want to have, how good it will feel to squat 225 for reps, the looks I will get when I’m where I want to be. How strong I will feel.
Conversely, when I want to cheat on my diet, I mentally walk myself through the process…what the item in question will smell like, taste like–and how I will feel afterwards. Then I go brush my teeth.
Rewards. I built an elaborate system of rewards for physical and dietary goals. First off, on the most basic level, a week of dialed-in nutrition yields me a free day. This works really well for me, and I find there is no craving I can’t defer until the weekend.
Secondly, weight loss and physical goals (i.e., losing 10 pounds, completing a certain number of pullups, etc.) net me presents. I made my first reward a big one, and now every time I look in the mirror, I see diamond earrings that represent the first 20 pounds lost. It’s a sweet sight. Obviously, tailor that to what’s appropriate for you.
Finding exercise you love. I took up racquetball, which I adore. Now all my cardio, some of which is admittedly not so fun, is perceived to be in support of being a better player. That helps!
Community. Check in here often. The rest of the world is not participating in this endeavor, or they’re doing it in a really stupid way (i.e., subway, slimfast). Every day, while I eat my never-ending chicken breast, I read the forum to see that there are others facing the same struggle in an intelligent and thoughtful manner. Posting your diet for critique nets extra bonus points and helpful feedback.
Foodlog. It keeps you honest and accountable, and gives you a history of what works and what doesn’t.
Momentum. Nothing breeds success like success. Make a commitment to yourself that come hell or high water, you will stick to your food and training plan for two weeks. No deviating. And that then you’ll re-evaluate. I suspect that (a) you’ll find it’s not as hard as you think; and (b) you’ll start to see results, which will make you want to continue. Along your path, pay attention to the mirror. Spend a little extra time cataloging your physical changes. Two weeks. You can do ANYTHING for two weeks.
I wish you success.