It's been more than two decades since Kobe Bryant graduated from Lower Merion High School, a public school in the suburbs of Philadelphia. But the retired NBA star, now 40, still remembers one teacher in particular: Mr. Fisk, who taught English.

"He had a great quote: 'Rest at the end, not in the middle,'" Bryant told podcast host and best-selling author Lewis Howes on an episode of "The School of Greatness." "That's something I always live by."

Hard work has been a key ingredient in Bryant's recipe for success since he was a teen. The emphasis on perseverance started as a defense mechanism, he told Howes: "In middle and high school, a lot of the kids that I was playing against were inner-city kids. They're looking at me as if, 'OK, this kid is soft. He's from the suburbs of Philadelphia. His father played in the NBA.'"

The challenge for Bryant became, "How can I mentally figure out ways to break you down? How can I show you that, no, I have the edge?"