Wow. I'm actually a little saddened that you feel this way after losing 80 lbs. I thought eventually my own thinking would work itself out!
Seriously though, yes, I definitely think this way. In fact, just last night I slept really heavy or something. I woke up and just ached. I felt like a big brown bear had crawled in and slept on top of me in the night. Oh, it hurt to move, I felt so heavy. I lay there thinking, oh no, all the weight came back on last night. I ran through what I had eaten the day before. Then when I weighed in, I had actually lost .6 pounds from yesterday. So I don't know why I ached so. But it's a very real fear. It's absurd to think I'd put back on nearly 30 lbs in one night even though I was on plan, but there it is. It was a real fear.
I fear very much that this weight loss is going to stop. But I have tricks in my back pocket. When/if I stall out, first I'll increase my calories. If that doesn't work I'll do Phase I of South Beach. (Been there, done that, know I could do it again.) If that doesn't work I'll add exercise. If that doesn't work...well I'll cry! LOL! But seriously, if that doesn't work I think I'll focus on maintaining to re-set my body, if there's any real science to that, and then I know that would have to work.
Hang in there. We're all right there with you.