Does this happen every day? If not, then maybe you just declare it a "cheat meal" or "cheat day" and vow to do better the next day. If you constantly feel deprived about what you're (not) eating, this may not be the right diet plan for you.
I'm of a normal weight, though I'd be happier 10 lbs lighter, like I was before I turned 40. I am mostly a good eater, but I have days where I eat like crap. I just write it off and move on.