Your teacher hears your improvement before you do. Trust the people who listen to you every week.

You are listening from inside, which is the worst seat in the house. All you hear is the gap between what you wanted and what came out, while somebody who hears you weekly is comparing this week to last. When they say you have improved, that is a measurement rather than flattery.

Have the person who hears you every week tell you what has changed, specifically, and then believe the answer. Write it down, because you will not retain a compliment you do not already agree with. On the days you feel like you are getting worse, read it again.