Wow Jack, that must have felt amazing, to get through those feelings and have something good happen as a result. I can't entirely relate to having those feelings after surgery, as I haven't had it yet, but I can see myself feeling those same anxieties for a while. What you said makes sense, it seems to be a combination of things, always having needed to hide that area in the past, scars of course could be a concern.
I had a sort of similar experience. I went swimming last year, which is obviously a huge deal for someone pre-op. I only did it to make my girl happy, because she kept eyeing this bathing suit but didn't want to swim alone (later found out she has a fear of water). I wore swim trunks and a black T shirt. Oh but it gets worse, I had a binding injury...I tried to bind to swim, but my brain was screaming out in pain, so I went back into the hotel room and changed into a sports bra. I was worried but decided to go back in so as not to cut the swimming short for the others. Now, my chest is small in proportion to the rest of my body, when I was skinny they were A cups, now they are bigger but I have a big belly...I still worried everyone would think I was female and I hated the idea of drawing attention to my chest. But I went in, and ran into a few people who all gendered me as male anyway. One kid even asked me why I was wearing a shirt in the pool, like, dude, why would you do that?
I still hated having my chest, but it felt good to go into the pool and be seen as male in spite of it. Not quite as victorious as your Taekwon-Do story but maybe I will have my own in a year or so.