Have any of these situations ever happened to you, and do you know why they do?
You decide to cheat on your diet. You go into the grocery store for a box of cookies. Before you make it to the cash register, you think, "I shouldn't be doing this. I will regret this later. I will be happier if I don't do this." However, because you already feel guilty for having made the decision to cheat, you go ahead and eat anyway--like just choosing to overeat is the same thing as going through with it. WHY?
You decide to cheat on your diet. You have the jar of peanut butter open on the counter in front of you. Midway through your second spoon you think, "I will be ok if I just stop now. Why don't I close this jar and be done with it? this doesn't even taste that good!" However, you have half the peanut butter left on your spoon and so you finish the spoon because it's easier than finding some other way to get rid of it. Before you know it, you have plunged the spoon back into the jar and the cycle begins again. Why? why can't you put down the spoon?
You have decided to stick to your diet. You are somewhere where they serve you the food, and you have no choice over portion sizes. You are served, say, a piece of chicken. You dutifully remove the skin and eat the chicken. You finish your beans, you drink some water...you are actually full. However, the crispy friedness is still sitting on your plate. Surreptitiously you eat all of it in one bite. WHY?
These are hypothetical, but real-life situations that happen to me all the time. I think logically, I mean well and something in my brain just blocks out the logic and the sense. what is that? why?

(okay disgusting thought).