You've probably heard of "aversion" therapy--that's where you take some behavior you're trying to stop and pair it with an immediate negative experience (like an electric shock) so that your brain starts associating that behavior with the negative experience. Alcoholics, for example, sometimes take a drug called Antabuse, which literally makes you sick if you take a drink.
This is a little harder to do when the behavior you want to stop is a mental behavior, but sometimes using a little imagination and a powerful visual image can do the trick. For example, consider that silly mental behavior we all tend to engage in once in a while (if not more often): the "I've already blown my diet for today, so I might as well keep eating" game.
Obviously, this is nothing but a flagrant rationalization. If you stopped for even a second to think about it, you'd realize that going even further over your calorie quota makes no sense at all. It just makes repairing the damage even harder. But the real problem here is not that you use rationalizations that don't make sense. The real problem, of course, is that you want
to keep eating, and that's the thing you need to change. Once you do that, the rationalizations and excuses will disappear on their own.
Unfortunately, just telling yourself that your rationalization doesn't really make sense isn't usually enough to change the desire to keep eating into something else. For that, you need to connect the desire to some kind of undersirable experience or image, so that your brain will be desperate to go somewhere else when it pops up.
You could do something like hit yourself in the head whenever the urge to keep eating comes up, but that would be pretty inconsistent with the healthy lifestyle approach we recommend here at SP. This is where you need to use a little imagination to get the job done. Instead of fighting the urge, or telling yourself how dumb it is, try taking it to the extreme, in your mind. Imagine, for a minute, what it would be like to never have to stop eating, and see how that makes you feel. Is that really what you want, or how you want to be?
For those of you who have trouble imagining something like this, here's a link to a video you can use to get your creative juices flowing: