What's so magical about solitude? In many fields, Ericsson told me, it's only when you're alone that you can engage in Deliberate Practice, which he has identified as the key to exceptional achievement. When you practice deliberately, you identify the tasks or knowledge that are just out of your reach, strive to upgrade your performance, monitor your progress, and revise accordingly. Practice sessions that fall short of this standard are not only less useful - they're counterproductive. They reinforce existing cognitive mechanisms instead of improving them.