Ah this is the problem with treat days. I know that is what would happen for me as well. I try and think how a normal skinny person would eat and I am sure they wouldn't just eat because they got weighed. Don't mind going off track for holiday or special occasions as am sure they would do that and then get back to eating sensibly. Just draw a line under it you have the rest of the week now. Just think of those flowers you wouldn't throw away a bunch of flowers just because one was dead. You would just throw that one away.