I got a comment on the Fat Loss for Idiots review from a fellow that had cheated the night before on his diet. Here is part of how I responded
The best thing to do is to jump right on the diet this evening and tomorrow. There is no way that you can undo what you did in your eating but remember that it is only day 2 and you are just getting used to the diet, these things can and will happen but it is youor reaction to them that is important.
Now that you know that dinner is your tough time it is probably a good thing to look at your successes over the first two days and figure out what you will od about dinner. Most of us are used to having a big dinner and if you can convince yourself (lying to yourself is fine) that dinner is just another meal and a weak one at that since it is so close to sleep then maybe you can have a better plan for how to tackle dinner tomorrow.
What do you do now?
Often we try hard on a diet or exercise program and in just a moment we lose our concentration or our willpower and then we feel we have failed and need to start over.
In fact if you have lost or even been successful for a day it is easy enough to leverage that success. What did you do right? How could you have avoided that cheating? Tony Robbins once said in a tape series “Success leaves clues” all you need to do is get better at avoiding the situations that cause you to cheat.
Continue your diet
So no, you do not have to restart a diet or even to wait until the next day to get back on the horse. Your diet is everything that you eat so if you ate too much dinner or the wrong dinner then just continue on.
If you eat some huge grease laden breakfast then you probably will not feel like eating lunch but remember to at least have a snack because you want your body to know that it is not a feast or famine type lifestyle that you are living anymore