I hear you, definitely the best thing to do is go straight back onto the diet, I don't think that much harm would be done with one meal, I'd be interested to hear the answer to this too.

The danger is once you actually stop and eat something you shouldn't it starts the cycle again and you turn around a week later and have to start from scratch. So better not to give into temptation to start with - easier said that done of course! sheeesh this is tough