Andre Agassi started his tennis career “in diapers” and ended it at age 36, having won eight Grand Slam titles. Married (to fellow champion Steffi Graf) with two kids, he now oversees a foundation and a charter school in Las Vegas where accountability is the mantra. No courts on campus, though. “The idea that I succeed at your demise doesn’t fit the culture,” he explains.

A version of this article appeared in the October 2015 issue (p.136) of Harvard Business Review.