Practicing, and the benefits it brings, is of interest to many fields - not just music. Continued practice in music, tennis or any other endeavor will continue to yield benefits, even after we "learn" the thing we are practicing.
“Why do I have to keep practicing? I know it already!”
That’s the familiar wail of a child seated at the piano or in front of the multiplication table (or, for that matter, of an adult taking a tennis lesson). Cognitive science has a persuasive retort: We don’t just need to learn a task in order to perform it well; we need to overlearn it. Decades of research have shown that superior performance requires practicing beyond the point of mastery. The perfect execution of a piano sonata or a tennis serve doesn’t mark the end of practice; it signals that the crucial part of the session is just getting underway.
Read this (brief!) article on "The Neurological Benefits of Practice" — and then get back to practicing!