Most musicians at one time or another have problems "letting go". Even if they have developed their understanding of music and their technique, "something" holds them back. This can often be traced to a simple though ultimately irrational fear. Fear of what? Maybe they're not as good as they think they are. Maybe they're not as good as their friends and relatives say they are. Maybe they don't stack up to the competition. Whatever the fear, it is certainly destructive. How many people who have the "right stuff" refuse to believe it and act upon it.
Music ultimately is not a competitive sport. It is a pathway of self expression. How many people have said "I get it", musically speaking. But the problem is that they don't "get" themselves.
Putting your self into the music as fully as possible starts to break this negative tendency. Not worrying about the reaction of others is an important step in developing the skill of "letting go".
Don't fear mistakes! Fear not taking chances!!!