Hun don't be upset at yourself, it happens, and the guilt is so counter-productive. I know it's easy for me to say that but you're talking to someone who had a pretty good food day, then ate four slices of toast and marmalade last night!
I've learned that the only way not to do it is to not have the bad stuff in the house in the first place - and I like your tactic of having another light dinner to fill you up x.