Watch your first reaction to feedback before your polite face kicks in. That flash tells you what you still need to work on.

A half-second passes before the polite face arrives, and that half-second is unmanaged. Whatever flares in it, defensiveness, shame, a flash of anger at the person, is pointing at something you half believe about yourself. The polite response afterwards is socially necessary and tells you nothing.

After the next piece of criticism, write down what the first flash actually was. Not what you said, but what went through you before you arranged your face. Then look at what it was protecting, since that is usually the real work rather than the detail they mentioned.