Keeping a daily log of your diet is a great way to stay on track. When you're honest with yourself and write down everything you eat, you'll think twice about eating too often or the wrong foods. It will help you stay focused on your goals.
I start out the day by writing a positive affirmation on the top of the log sheet. And at the end of the day I write my feeling on how I did - I always write positively. If you haven't kept a diet journal before, give it a try, it's very simple and very motivating.