You've probably heard the saying "All work and no play makes Jack a dull boy." I suspect that most people interpret this as a comment on Jack's personality: He's "dull" because all he can think or talk about is work.

But that's not what the saying actually means. According to the latest neuroscience, overwork makes your brain "dull" in the sense of being the opposite of "sharp." Overwork, in other words, kills your creativity.

Scientists studying brain scans recently discovered that moments of creativity take place when the mind is at rest rather than working on something. And since creative approaches are so crucial to success, workaholics are working themselves out a job.

Here's how Brigid Schulte, author of Overwhelmed: Work, Love, and Play When No One Has the Time, characterizes this phenomenon:

Neuroscience is finding that when we are idle, in leisure, our brains are most active. The Default Mode Network lights up, which, like airport hubs, connects parts of our brain that don't typically communicate. So a stray thought, a random memory, an image can combine in novel ways to produce novel ideas.

This is not to say that people who are "all work" don't get things done. Quite the contrary--they're great at checking off the busywork boxes. But when it comes to thinking of new approaches--working smart, not hard, as they say-- workaholics are worse than useless.

I'm sure you know a few of these folks: always on a device, always doing a project, always go-go-go. They're proud of the fact that they're stressed to the max and look down on anybody who's not similarly overworked.

Of course, it's long been known to medical science that stress from overwork causes major health problems, but the business world has tended to treat that as an acceptable trade-off. A health risk is tolerable if long hours are necessary to achieve success.

But what the research is now saying it that there is no trade-off. Long work hours don't make you more successful. Instead, they make you sick and worse, they make you "dull"--in other words, mediocre and uncreative.

Unfortunately, the myth that overwork equals success has become so ingrained in American corporate culture that it's going to take a lot of courage to buck conventional wisdom, even when neuroscience has proved that "wisdom" is demonstrably false.

So my advice to you (and frankly to myself as well) is to summon the courage to relax. Be brave enough to give your brain the leisure it needs to carry your ideas, your career or your company to the next level.