The smartest CEOs insist their workers take time off--for their good, and the company's.

Great employees are hard to find. And by "great," I don't just mean a gifted coder or a skilled data I mean a relentless worker. I mean a "road warrior," who takes ownership of projects and doesn't rest until they're done.

Here's the thing with those star employees: They know you cherish them. They know you appreciate their all-out effort. So they're not going to take vacations--unless you tell them to. And if they don't take vacations, they're imperiling both their health and their long-term performance. "The ill effects of refusing to go on vacation, documented in research, include fatigue, poor morale, heart problems and reduced productivity," reports Sue Shellenbarger in a recent Wall Street Journal article.

How, then, can you compel your most dedicated employees to take time off? Shellenbarger's article offers a few examples:

• Evernote pays employees $1,000 to vacation for at least one week.
• HubSpot enforces a minimum two-week vacation for all employees.
• FullContact pays employees $7,500 a year to partially finance a vacation.
  
  Yes, yes, I know what you're thinking: "How nice for all of those investor-backed, forward-thinking tech companies with the ultraslick compound-word names. What a luxury it is, to afford to subsidize all that off-time. But any real startup in the trenches would never be able to pay for that."

Perhaps. But that doesn't let you off the hook. Even if you can't pay your staffers to take time off, you can still create a workplace culture in which your great employees are comfortable walking away for a little while.

At HubSpot, for example, salespeople are allowed to reduce their quotas twice a year, Shellenbarger reports. That helps salespeople feel comfortable about using their two-week vacations. They no longer fear that doing so will make them fall behind on their workload or cut into their compensation.

You can give your own employees a comparable safety valve--a twice-yearly choice to lower their workload or opt out of requirements. By doing that, you'll remove one of the barriers that prevents hard-working employees from getting away. "A heavy workload and fear of returning to a big backlog are major reasons employees don't take all their vacation," writes Shellenbarger. "Some may feel vacations simply aren't worth it."

Another way you can compel your hardest workers to take time off is to sell them on how much the time off will ultimately improve their performance. "If we can train ourselves to take regular vacations--true vacations without work--and to set aside time for naps and contemplation, we will be in a more powerful position to start solving some of the world's big problems," asserted Daniel J. Levitin, director of the Laboratory for Music, Cognition and Expertise at McGill University, in last Sunday's New York Times.

Whatever you tell your employees, the key is that they listen--and leave. Your employees need to feel comfortable going away. And that starts with letting them know that the company will be fine without them--at least, for a little while.