The musician practicing quietly is giving the future performance somewhere reliable to stand.

Practice is invisible, and it is where a performance is actually built. Hours of dull repetition, alone, with nobody listening, produce the security that lets somebody play in front of a room without their hands betraying them. What looks like ease on the night is the surface of that groundwork. The quiet work is not preparation for the real thing so much as most of it.

Give the unglamorous part of whatever you are learning a regular, protected slot. Judge those sessions by whether they happened rather than by how they sounded.