"If you are a duffer at golf, say, and make the same mistakes every time you try a certain swing or putt, 10,000 hours of practicing that error will not improve your game. You'll still be a duffer, albeit an older one. No less an expert than Anders Ericsson, the Florida State University psychologist whose research on expertise spawned the 10,000-hour rule of thumb, told me, "You don't get benefits from mechanical repetition, but by adjusting your execution over and over to get closer to your goal."2"