There is a thing called professional development. A professional is always working on improving - be it in sports or any other career.
Michael Jordan spoke to journalist about working overtime on his free throws. This was the season before he retired. He never stopped trying to be better than he was.
I'm no Michael J, but even I'm trying to improve myself. I completed my PhD in the late 90s, worked at IBM's Watson Research Center, have 20 plus publications and patents but I'm also taking online college courses. For example, I'm taking a course in Social Network Analysis from Stanford. I have my homework due this Friday. I'm also relearning how to play the guitar with my daughter.