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An accountant who fills out spreadsheets at the beach, a dog groomer who always has time for one more client, a basketball player who shoots free throws to the point of exhaustion.

Every profession has its share of hard chargers and overachievers. But for some workers—perhaps more than ever in our always-on, always-connected world—the drive to send one more email, clip one more poodle, sink one more shot becomes all-consuming.

Workaholism is a common feature of the modern workplace. A recent review gauging its pervasiveness across occupational fields and cultures found that roughly 15 percent of workers qualify as workaholics. That adds up to millions of overextended employees around the world who don’t know when—or how, or why—to quit.