I try to remember that the world will not end just because I had an extra slice of pizza or scoop of ice cream. Yes, I do get disappointed that I'm that far away from my goal, but, honestly? It's ok. all that matters is that I don't give up, and use a one time wagon fall-off as fodder for wagon avoidance...
so get back up there and do it!
once you know you can, and that you have control, and you CAN say "NO", there's nothing stopping you.
you go girl.