History's great achievers have always managed themselves. That, in large measure is what makes them great achievers. They were once rare exceptions, but in today's world most of us will have to learn to manage ourselves. Peter F. Drucker, author of Management Challenges for the 21st Century, explains that success in the knowledge economy comes to those who know themselves - their strengths, their values, and how they best perform. This article, which originally appeared in the March-April 1999 Harvard Business Review, is offered in audio form exclusively through Audible.