10,000 hours – Katy Ledecky, Yo Yo Ma, Simone Biles, and many others understand. There is a threshold of practice that raises one’s level of performance to expert. And then a dedicated persistence and perseverance in that practice is needed to maintain that level of expertise. Last century, when I was in college I had reached 10,000 hours and more. I competed at a national level, in the deep end so to speak, where lots of people competed in races that were resolved in tenths or hundredths of seconds.