Jigglefree, I did the exact same thing today. I was out to lunch at a Brazilian restaurant, and I ordered what looked like the healthiest thing on the menu: shredded chicken in a crepe with a tomato-based sauce, white rice and black beans on the side (I held the melted cheese at least). It was huge and I know I should have cut it in half right away and taken a doggie bag with me, but it was so good and I couldn't stop. I ate the whole thing. I just wanted to feel that nice full feeling. So, I understand your frustration today. I ate a big green salad for dinnner, and did a little bit of extra cardio to "pay" for it, and know that tomorrow will be a fresh opportunity to practice moderation. I did try to notice how my stomach felt after I ate it, and asked myself, "is this feeling in your stomach worth delaying your progress?" And I was able to answer "no" with conviction. The next time I am tempted to go crazy I will remember that.
Good luck, and you didn't mess up nearly as badly as I did today, so hopefully that will make you feel better!