If you're struggling to feel motivated about anything from starting a difficult project to sticking with your workout routine, call yourself what you aspire to be. Following this rule can help you reach your goals for one simple reason: Identity drives behavior. That insight comes from best-selling author, executive coach, and entrepreneur Eric Partaker, who co-founded the Chilango restaurant chain and helped build Skype's business in the U.K.

"I get reminded about the power of identity-driven behavior by my children," he said in a master class at this week's Web Summit conference in Lisbon, Portugal. For instance, he once bought his 8-year-old son a Captain America shield. "He loved it, and he immediately became Captain America," Partaker said. "I didn't have to sit him down and say, 'You've got the shield. Now, here's your Captain America behavioral training.' None of that was necessary because as children we know that identity drives behavior. As adults, we forget this." And yet it can be a very powerful self-motivating tool, he said. Because if we give ourselves the identity we aspire to, that identity can create the behavior we want.

Partaker uses this tool on himself every day by setting three smartphone alarms. The first, which goes off every morning at 6:30, says "World Fitness Champion." "I'm not a world fitness champion," he said. "I was picked last for sports in school. But that's the version of me that goes to the gym every morning." In fact, he said, it motivated him on the day of the presentation. He had briefly considered skipping his workout so he could arrive really early. "And then I thought, 'World Fitness Champion,' and I went to the gym."

At 9 a.m., a second alarm goes off that says "World's Best CEO." "How decisive, inspiring, and reliable do I need to be to be at the helm of my company and to also lead the entrepreneurs and business leaders that I coach and mentor?" he said. The alarm is a reminder to him to live up to that version of himself. "It makes me show up differently throughout my day."

World's Best Husband and Father.

At 6:30 p.m., the most important alarm goes off. It says, "World's Best Husband and Father." "I'm not the world's best husband and father," Partaker said. "I really needed this one most of all, because when I would get home, my wife might ask me to help her with something and I'd say, 'Let's do it on the weekend.' The kids might want to play and I would put that off and say, 'I've got to work on a few more emails.' " The alarm reminds him to do things differently. "It prompts the question: How would the World's Best Husband and Father walk through that door?"

The whole point of this is intentionality, he said: "Identity-driven intentionality in the areas of life that matter most." He added that this approach is proven to bring longer-lasting change than just focusing on changing your behavior, which Partaker calls "trying to build yourself from the bottom up."

There's a growing audience of Inc.com readers who receive a daily text from me with a self-care or motivational micro-challenge or idea. Often, they text me back and we wind up in an ongoing conversation. (Interested in joining? You can learn more here.) Many are entrepreneurs or business leaders, and the ones who take on the identity of what they want to be are often the ones who are most successful.

To achieve your full potential in the three areas of life that matter most -- health, wealth, and relationships -- Partaker says, "Choose your identity. Give it a name. Put it on your phone as an extra cue so you know what superhero version of yourself you're stepping into at each time of the day. So you can close that gap between the current version of yourself and your best self." What name or names will you give the best version of you?