Are you living an "essentialist" life? Most people aren't. Greg McKeown, author of the new book Essentialism: The Disciplined Pursuit of Less (available for sale April 15) describes essentialism as "living by design, not by default."

The basic idea, as McKeown details in the video above, is to reduce or eliminate commitments to things that aren't really necessary.

"We've been sold this idea that we ought to be supermen and superwomen who sleep four hours a night and can just fit it all in," McKeown says. "We've been oversold the value of more and undersold the value of less."

The most effective way to embrace less is to say no more often -- to bosses, colleagues, spouses and even our kids. Of course, that's easier said than done, and while people may agree with your overall goal, they may push back when you say no to them.

Still, most people today take on too many responsibilities -- at work, at home, with friends -- and the more time devoted to "non-essential" activities, the less productive we become.

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McKeown provides one example of a Silicon Valley executive who was floundering in his job because he was reluctant to turn down extra work assignments and meetings. As a result, his stress levels rose and his effectiveness declined. He had turned down an early retirement package that was offered to him -- a sign that his employer was politely showing him the exit - and he knew that to save his job, he needed to change his situation -- immediately.

The exec's fortunes changed only after he carefully evaluated requests, stopped volunteering for last-minute presentations and assignments, and committed to projects that were truly important to his work. The approach paid off: his bosses and colleagues started respecting him more and there were no negative repercussions. His performance ratings went up and he received one of the largest bonuses of his career.

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People don't realize that we "can push back, we can negotiate," McKeown notes. "If we don't prioritize our lives, someone else will do it."

McKeown admits that becoming an essentialist takes work. "It's not a process you undertake once a year...it is a discipline you apply each and every time you are faced with a decision about whether to say yes or whether to politely decline," he writes. Essentialists learn to say "no" to a good opportuniies because they're willing to sacrifice their efforts and time for something even better.

How to start? McKeown recommends that Individuals take 20 minutes once a week to ask themselves: what is my priority for the week? And it should be one, single priority, not several priorities. "We can do lots of things average or we can do a few things tremendously well," McKeown says. "If we do few things better we can make a higher contribution."