Diets don't work. Why? We go on them, we go off them, back on, try another one, etc. How about adapting a healthier way of living, a healthier lifestyle?
This means that you will need to stock up on whole grains, fruits, vegetables, lower fat meat or other proteins (chicken, fish, beans, peanuts, tofu, other nuts) and lowfat dairy. Keep healthy items stocked in your kitchen. Have carrot sticks, apple slices, chopped celery, fresh berries, orange slices, etc around when you just want to munch on something.
This is not something that you go on and off, you do not need to avoid a whole food group. It's all about moderation. And when you do go to a party or have that piece of cake you can enjoy it because you will know that you have been eating healthy, most of the time.
If you and your kitchen are healthy, you will not fail!