Marle-
I, too, feel the emotional hangover. It feeds into the codie feeling and then seems to jump start a vicious cycle- we feel crappy for acting crappy and that makes us continue to feel crappy.
I think it's hard to be our own voice of reason- but maybe your rational voice can talk you down- speaking gently and calmly tell yourself that your progress is NOT erased and that it is okay to falter- that is what helps keep us stepping. Progress not perfection.