Which advice works best for you? "You're thinking too much. Just play!" or, "Think about what you have just played. Listen to yourself. It's a mess!" For some, the need is refinement and detail work. Others desperately need to loosen up and consider the music. While some need to get to the practice room, others need to get to the stage. Obviously both are necessary.
I remember Arnold Jacobs insisting on the playing mechanics being studied and well executed, but he never stopped there. All the parts must serve the musical whole. The actor studies the script, practices his lines, prepares the delivery. But when the curtain goes up, it's showtime. His responsibility is to become his character. Practice is over as it's now all about performing. Both types of preparation are vital. The key is learning to use both to our advantage.
The nature of school curricula seems to be heavy on practice and light on performance. And that is probably as it should be. There is a season for learning, and there is a time to play. The most effective learning however takes place in concerts. Showtime teaches us what we need to do in the next practice session. Performances provide our practice agenda. We need a good balance of both practice and performing. All practice and no shows make Jack a very dull trumpet player. And all show and no practice also makes Jack a very dull trumpet player.
Sometimes it is best to think more, but sometimes it is better to think less. Think about that. What a life! We work, and then we get to play. Not a bad profession. In most jobs they never get to play.