I have a theory for life. I call it the forbidden cookie theory. It is that if you deny something to youself, it will immediately become more desirable. If you give up cookies for Lent because you love them so much, they will become even more desirable for that month than they have been previously. Someone who can easily go a week on salads, rice, and other foods suitable for Passover will have cravings for bread and pasta for that holiday, simply because all they can eat is matzo. It is because thinking about denying yourself something is thinking about that thing.
It works in interpersonal relationships roughly as the song "Let Me Go" says: Let me go and I will want you more. As soon as you say that something can't happen, it becomes endowed with an almost wistful power over you. And even a light friendship can be devastating if instead of petering out it is abruptly cut off. People don't like sudden change, and they don't like denial.
I think this has applications to dieting. It's how weight watchers works. Tell people that they can eat anything they want, but that they should keep track of their calories and fat intake. When people realize that they have the choice, the cookie isn't forbidden, but instead carries with it repercussions that while not monstruous are present -- they can choose not to have the cookie because they don't want to, not because of an arbitrary rule they set up. And generally speaking, if you follow your cravings and do things in moderation, your body will tell you how to live healthily. It's evolved to do that well.