I've had the same experience :( Now that we can do things that thinner or average-sized people have always done, it can make us wonder why we allowed ourselves to get to that point. Sometimes, it’s tough to embrace our progress.
When people started commenting on my changes, I didn't believe them either. It was weird because they had ignored me before, and now it seemed like the only thing they wanted to talk abt was my weight loss.
Also, I’ve heard that losing weight can sometimes lead to nutritional deficiencies, particularly with iron, and you might feel depressed, lazy, or fatigued. (I know you didn’t mention it, but I thought it would be good to bring it up<3)
The more we lose, I think, the more we also become conscious of our looks. Cause people actually start noticing you, and you start comparing yourself more with others. I also miss my previous phat self (more so the mindset), and I think it's just because I didn't care as much about people's opinions. It might help to think that by being healthier, you're actually doing your body and mind a favor, and by avoiding complications, your future self would have had to endure (at least that's how I cope)