It's easier to think of a
diet as something that you'll stick to for life, not something that you have to punish yourself with for a while in order to reach a desired weight. Just concentrate on being healthy, and I'm sure that this time you can succeed for life.
Don't mean to sound preachy, I just love giving advice =D
Joining this forum has really helped me to stick to my
diet, so I hope that it works for you, too! You could start a journal to track your daily progress, thats been my favorite portion of the site so far.
The most important thing is that you've really decided to change, and that's the biggest step of all!