We schedule every minute of our day, pride ourselves on forgoing breaks, and berate ourselves for the slightest moment of distraction. We view sleep, sickness, and burnout as unwelcome weaknesses and idolize those who never seem to succumb to them. This view, however, fails to recognize that efficiency and effectiveness are not the same thing.

As a practical matter, it is impossible to keep everyone in the organization 100 percent busy unless we allow for some buffering at each employee’s desk. That means there is an inbox where work stacks up.”

DeMarco defines slack as “the degree of freedom required to effect change. Slack is the natural enemy of efficiency and efficiency is the natural enemy of slack.” Elsewhere, he writes: “Slack represents operational capacity sacrificed in the interests of long-term health.”