Lyn - I hear ya! I understand totally how you feel. I am sorry you are feeling so frustrated.
It's what can happen. We are 'eaters' - it's what we do...it's how some of us deal with life. Sometimes we are better at food sanity than others.
But, the main thing is we can never stop trying (again).
Sometimes, when I need to 'try again' after a gain... I switch it up a little bit...just to make it fresh.
We can't change anything we've already done. All we can do is try and learn from it. So... my philosophy is: learn from the past, plan for the future... but, take one day at a time.
Hang in there... you'll get there.