In an interview with Sonny Rollins one can read that this saxophone giant doesn’t think about anything while he’s playing, but what his unconscious mind wants will be achieved. Thinking and playing don’t go together!
Perhaps you have had the experience that as soon as a thought arises (“That’s going well!”) immediately your playing goes off the rails (or youe are falling on your face when skiing). You have no time to think if you are busy with making music (or doing anything else similar where you need to be in the moment!) Your conscious self is too slow and can in no way multi-task.
In the state of flow there are no thoughts, there is no time and everything comes of itself. There is a lot that has been written about this state and it gives an idea of what you must do as a musician to achieve this state.
What matters to me is that your unconscious must speak. There is an enormous database of (musical) knowledge and skills there which you have acquired and there lies the entrance to creativity and inspiration. In order to gain access you must first put your conscious self out of the way. Your conscious self will always want to understand everything, compare and control, thus it is not so easy to turn it off. In our society we are accustomed to doing things on a very conscious level, but much less accustomed to setting our conscious mind aside!
In my saxophone lessons which I give to adults this is often one of the reasons why the notes do not become music. The focus is on the “little balls on sticks” and understanding is precisely what hinders them from coming to life and this seems paradoxical. Varying and improvising does require that the notes (and more than the notes) are well learned. However, they must be placed in their musical context.
So, let go! For rational control freaks it is most often harder to learn, but music is a beautiful way to learn it!
In order to learn to let go you must study the music well and, as has already been said, in the proper manner. By practicing these skills end up in your unconscious and consequently you don’t need to think anymore while playing. Studying well is thus a condition to be able to perform without bothersome thoughts. In addition you want to study in a creative manner. You create then open automatisms: automatisms with more performance options. You can the play more in the moment and keep the music alive.
Once on stage, it is important to put your head in the backseat and to give yourself over to the music. Your skills will be freed and in addition you can free your inspiration. You will even amaze yourself with your playing!