From a Washington Post column by Sally Jenkins headlined “How Michael Phelps learned to make the right calls”:

For 20 years, Michael Phelps swam for five miles a day, six and seven days a week, trawling through resistant liquid, staring at a black line on the pool bottom. Phelps swam on Sundays and his birthdays. “Nobody else did that,” his coach Bob Bowman said. When Phelps’s chest began to bloom with gold medals, outside observers attributed it to a genetic gift. But that missed the most important fact about Phelps, one with significance for all of us. “The thing that made him great was the work,” Bowman observed.