Everyone thinks their own strike zone is fair. That’s why leagues hire umpires.

Self-judgement drifts, and it drifts in a flattering direction without anybody intending it. Each individual call feels obviously correct from where you are standing, which is how a whole room of people can all be certain and all be slightly different. Outside judgement exists not because people lie but because nobody can see their own position.

Find the equivalent of an umpire for something you care about: a mark scheme, a timer, a coach, a friend who will tell you straight. Use it regularly rather than only when you feel strong.