You can do anything - but not everything.

You know the drill. It's Monday morning. You arrive at work exhausted from a weekend spent entertaining the kids, paying bills, and running errands. You flick on your PC -- and 70 new emails greet you. Your phone's voice-mail light is already blinking, and before you can make it stop, another call comes in. With each ring, with each colleague who drops by your office uninvited, comes a new demand -- for attention, for a reaction, for a decision, for your time. By noon, when you take 10 minutes to gulp down a sandwich at your desk, you already feel overworked, overcommitted -- overwhelmed.

According to David Allen, 54, one of the world's most influential thinkers on personal productivity, this is the "silent trauma" of knowledge workers everywhere. We inhabit a world, he says, in which there are "no edges to our jobs" and "no limit to the potential information that can help us do our jobs better." What's more, in a competitive environment that's continually being reshaped by the Web, we're tempted to rebalance our work on a monthly, weekly, even hourly basis. Unchecked, warns Allen, this frantic approach is a recipe for dissatisfaction and despair -- all-too-common emotions these days for far too many of us.

Allen argues that the real challenge is not managing your time but maintaining your focus: "If you get too wrapped up in all of the stuff coming at you, you lose your ability to respond appropriately and effectively. Remember, you're the one who creates speed, because you're the one who allows stuff to enter your life."

Allen has spent the past 17 years helping busy people deal with all of the "stuff" in their lives. At seminars around the world -- at corporate functions and in corner offices -- he has preached his gospel of personal productivity. His online newsletter, "David Allen's Productivity Principles," has more than 7,000 subscribers. His book, "Getting Things Done: Mastering the Art of Stress-Free Productivity," will be published by Viking next January. He's even cofounded a software company, Actioneer Inc., that offers a range of time-saving tools.

It's been a long, strange trip from his youth in Shreveport, Louisiana. As a teenager, Allen studied Zen Buddhism and followed the path of Allen Ginsberg and the Beat generation. In college, he focused on philosophy and intellectual history, and became fascinated by thinkers who, he says, "seemed to have something cool going on, some bigger reality. I wanted to have some of the same experiences. So I did." (This was the 1960s: Use your imagination.)

Allen journeyed to the University of California at Berkeley to enroll in a master's program in American history, but he soon dropped that plan to study karate (he earned a black belt) and to begin "a 30-year quest for God, truth, and the universe." For work, he taught karate, managed a landscaping company, and helped to start a restaurant, among other jobs. But his real passion was the pursuit of self-discovery -- the personal-growth movement.

"There was a lot of flaky stuff on the edges, but at the core of the philosophy were some good ideas about how to live a life that's more in line with your values," Allen says. At the time, many HR executives were also broadening their interest in personal growth -- in helping people to think and to work together more effectively. Over time, Allen discovered a bridge between his fascination with self-understanding and his desire to interact practically with the world. That bridge was time management.

Allen has never been a naturally high-productivity person. ("I'm more of a party guy," he quips.) But he tried hard to change that. As he did so, he became convinced that time management was the key to personal freedom -- to greater self-discovery. He then became convinced that there was a pretty robust market for instruction in his newfound art. Finally, he became convinced that "God didn't really care whether I had money or not." More or less at that moment, he became a consultant.

In a series of interviews with Fast Company, Allen shared his ideas on increasing personal productivity in a business world that moves at warp speed.

If there's one thing that all of our readers probably agree on, it's that they have too much to do and too little time in which to do it. Why do so many of us feel that way?

There is always more to do than there is time to do it, especially in an environment of so much possibility. We all want to be acknowledged; we all want our work to be meaningful. And in an attempt to achieve that goal, we all keep letting stuff enter our lives.

The problem, of course, is that we also want to finish what we start. Much of the stress that people feel doesn't come from having too much to do. It comes from not finishing what they've started. That's why a lot of my work has to do with how people deal with their input -- email, phone messages, reports, conversations. Everything that isn't where it should be is an open loop, an incomplete, a distraction that slows you down. Your brain says, "Hey, that doesn't belong there," and you have to deal with that impulse.