Fellow teacher here! During my first 5 years or so teaching, I was so sensitive to negative feedback. Comments were overwhelmingly positive but I’d really wince at negative comments. I’ve grown a thicker skin since then, and more importantly I’ve come to believe in myself and I know I’m good at what I do. So, experience and confidence.
It’s true. I teach college kids, and a couple of years ago my class was taking a midterm. The room didn’t have a clock so I put my watch on the document camera display so they’d know how much time was left. A girl in the front row asked me what time it was, because she couldn’t tell time. After she turned in her test, thinking she must be kind of embarrassed about this, I told her I’d be happy to teach her how to tell time. She gave me a look like “ok, boomer” and said no thanks.