Old loop: I ordered the grilled cheese, so why not get the fries, too?
Switch to... One treat at a time. I'm indulging in grilled cheese, so I'll trade the fries for a salad.
Here's How: "The thought pattern is, I've already blown it for today, so I might as well keep going," says Janet Polivy, PhD, a psychology professor at the University of Toronto. She calls it the "what the hell" effect and says it causes people to devour so much food that they feel they'll never get back on track. To prevent this scenario from playing over and over, Polivy says, you have to redefine your idea of healthy eating. Allow yourself the occasional treat, as long as it's accompanied by smarter food choices like fresh fruit and vegetables. At roughly 500 calories, one melted cheddar on rye a week should hardly make you fat. Habitually tacking on a large order of fries, however, might.