Fast Company: The Art of Work talks about Csikszentmihalyi's concept of flow at work.
It's a condition of heightened focus, productivity, and happiness that we all intuitively understand and hunger for... People engage so completely in what they are doing that they lose track of time. Hours pass in minutes. All sense of self recedes. At the same time, they are pushing beyond their limits and developing new abilities. Indeed, the best moments usually occur when a person's body or mind is stretched to capacity. People emerge from each flow experience more complex, Csikszentmihalyi found. They become more self-confident, capable, and sensitive. The experience becomes "autotelic," meaning that the activity actually becomes its own reward. "To improve life, one must improve the quality of experience," he says. One of the chief advantages of flow is that it enables people to escape the state of "psychic entropy," the distraction, depression, and dispiritedness that constantly threaten them.