Yes, I think I have a suggestion that could be useful.
I think the problem is with your expectation that you should have resolved this ONCE AND FOR ALL.
Sometimes it happens that way, but generally that's not how we humans learn, heal, change, advance and grow.
Rather, we tend to progress in fits and starts. The general trajectory is in the right direction, but bumpy. We regress, then move forward, then plateau out, then move back or forward again. It's messy.
And if you have a rigid idea about how things should move in a perfect line forward, it can be discouraging enough to dump you right off the wagon and keep you there. ...Because the corollary to that there stinkin' thinkin' is, "Well, I've clearly blown it. I was fooling myself all along. I never made progress."
Trust me on this. It's typical that your reaction to this jerk of a guy sent you reeling backward. It doesn't mean you haven't progressed. Of course you have. You lost 40 pounds! And because you have, you can do it again – more easily this time, because you did it once before – as long as you don't let your unrealistic ideas about 'ONCE AND FOR ALL" and "FINALLY" get in the way, you're FINE.
I suggest you remove those phrases and that thinking from your head.
And instead, consider repeating to yourself an affirmation like, "MORE AND MORE, I'm feeling safer in the world and shedding unnecessary weight."
Or, "More and more, I'm going strong and feeling good,."
Or, "I know there will come a time when I will stay on course, true to my own goals and best interests, regardless of the behavior of others."
Tell those ideas to yourself in the mirror instead. They leave room for the inevitable fluxes and flexes of human progress, and don't set you up to feel like a failure.
See if you can consider yourself a work in progress, not a finished product. That's what we all are. Any therapist with any degree of experience will tell you, this is how we roll when we're healing old wounds and learning new ways to be. We watch this up and down stuff in our clients all the time.
I think of it like this: we're in your corner, holding your coat while you do battle with your demons, knowing that our job is to remind you that you're doing fine, making good headway, and when you get clocked by a surprise punch, it's okay - this is the most typical route to winning. Remember the larger context and get back up on your feet.
So, don't let that misguided expectation of perfect progress and final resolution, once and for all, rule you. Get back up, dust yourself off, clear your head and go the next round. You'll get there. Let me know how it goes. I'll hold your coat.