Your job as a musician is not to decide whether or not you are a good musician. Your job is to play music.
To play music today, tomorrow, and for a long time, you have to find a way to enjoy the process of making music.
You’re not going to ignore your mistakes. But they don’t go in the “bad musician” pile, they go in the “things to practice” pile.
So how do you improve as a musician without thinking about whether or not you are “good?” By taking music seriously and not personally.