I have a cartoon that a player constantly keep reminding himself “ Don’t screw it up!!”
It’s the same idea as “ Don’t think of an elephant!” because it means that it is already thinking of elephant. There is still the same object, “ elephant”. One of what I learned in school is that learning music includes even playing on stage. Even if the music is well practiced, but different from playing in practice, that could be nothing. In the first piano seminar in this semester, the guest lecturer said how to prepare for playing on stage.
Play for friends or teachers
Play as possible as you can for audiences if there is any chance for public or in school.
I remember when I’ve sat in front seat in Symphony Hall once, how nervous the cellist was, but once the orchestra began, he seemed naturally to get into the music, and get comfortable. It’s so impressed to me. I know that musician should be like that, and only when a player is doing so, one’s real music can be presented. I hope what to play in my head naturally without any concerning or worry about performance on the streets, in the train and in the practice room is played on stage anytime in the same way.