Science has recently demonstrated what many entrepreneurs always suspected: When it comes to success, there are more important factors than mere intelligence. In fact, the research of Angela Duckworth has shown that grit--passion and perseverance over long periods of time--may be the most important factor influencing the success of children, entrepreneurs, and employees.

Duckworth's research, summarized in her new book Grit: The Power of Passion and Perseverance, also suggests that grit isn't a fixed trait we're born with. You can grow to become grittier, and you can create an environment that fosters more grit. For Duckworth, the primary tactic she uses to foster a culture of grit at home looks like it would work just as well in the office.

It's called the Hard Thing Rule.

The Hard Thing Rule has three parts. "The first is that everyone--including Mom and Dad--has to do a hard thing," Duckworth explains in her book. "A hard thing is something that requires daily deliberate practice." At the office, most of us aren't demanding that employees, as part of their job, commit to one task that needs to improve through deliberate practice (that is, activities specifically designed to improve your skill, under the watchful eye of a master teacher). But imagine what would happen if all employees, as part of their job, committed to improve through practice in one specific area at a time.

The second part of the Hard Thing Rule might not sound that hard: "You can quit," Duckworth says. "But you can't quit until the season is over, the tuition payment is up, or some other 'natural' stopping point." For Duckworth, it's totally OK to switch from one hard thing to another, but to reinforce perseverance, that switch can't happen until a natural stopping point. On the job, this may be the end of a quarter or fiscal year or some other designated milestone.

The third, and possibly most important, part of the Hard Thing Rule sounds equally counterintuitive. "You get to pick your hard thing," Duckworth says. Meaning an authority figure doesn't command you to do it, you get to choose what your practice. At work, research has shown again and again the power of intrinsic motivation and employee autonomy.

Duckworth is quick to stress that, while she's been researching grit for a long time, the Hard Thing Rule does come with a few assumptions. But it's a rule that works well for her family. And from what we know about research into employee behavior, it looks like it could work equally well for you and your team.