For top business leaders, "work life balance" might seem like a pipe dream. That's especially true for the heads of middle market companies who are squeezed on both sides. Unlike many small-business owners, they can't simply shut down operations when they go on vacation, and unlike many Fortune 500 executives, they often have smaller staffs and less ability to delegate responsibilities.

But there's good news. Laura Vanderkam - author of the new book What the Most Successful People Do Before Breakfast - says work life balance is not only more possible than you think, it's also the secret sauce in your professional life. "To bring our best selves to work, we have to be our best selves," she says. "Everyone has certain non-negotiables that make life sustainable," and spending time with your family, exercising, or engaging in your favorite hobby enables you to thrive.

The first challenge to overcome in finding work life balance is a perception problem: Most of us overestimate how much we're actually working. "If you force people to keep track of their time, you find that almost no one consistently works more than 60 hours a week," she says, which leaves 52 waking, non-working hours (even if you sleep a full eight hours per night).

Part of the challenge, then, is figuring out how to use that time productively. That's why one of Vanderkam's top tips is leveraging the early part of your day. "Mornings are a great time for getting things done - particularly the important, but not urgent things that life has a way of crowding out," she says. "Exercise is a good example. I've found that people with intense jobs who exercise consistently almost always do it early in the morning. If you tend to work late, morning hours can also be a great time to hang out with your kids. Family breakfast is just as good for kids as family dinner."

She also suggests making more use of time-shifting (working at off hours) and working from home. "The fact that you don't have to be in the office to work is a major benefit for people who want full lives," she says. "An ideal set-up is to leave the office at 5 or so, spend time with your family, and then go back to work after they go to bed. People who can work from home on occasion - even just once a week - tend to be more satisfied with their jobs. To me, those upsides from technology far outweigh the downside of being always reachable. If you don't want to be on email, turn it off. Earth won't crash into the sun."

Finally, she suggests that you "use bits of time for bits of joy. If you've got 10 minutes before a phone call, you could check your email again. Or you could look at some artwork online, take a brisk walk around the office, say hello to a colleague, or text your spouse."

Ultimately, she advises that you should "figure out what your priorities are, and block them in first. Time passes whether you're aware of it or not, so playing offense with your non-negotiables is key to making them happen."

Dorie Clark is an NCMM contributor and a marketing strategist who teaches at Duke University's Fuqua School of Business. Learn more about her new book Reinventing You: Define Your Brand, Imagine Your Future (Harvard Business Review Press) and follow her on Twitter.