There's one piece of advice that entrepreneurs hear again and again. You need to find your "why." You need to figure out your purpose, and focus on that one thing that matters more than anything else. Your key advantage. Your unique skill. Your goal.

It sounds right, but people aren't that simple. We're all a mixture of multiple ideas and preferences and abilities. As we build our businesses, we want more than one thing: to succeed of course, but also to succeed in a particular way. We want to build successful businesses but we also want to raise happy families and give back to the community. We understand that we need to be serious and business-minded but we also know that if all we are is serious and business-minded, life is dull and lacks its spark.

We're not just entrepreneurs. We're human beings with all of the complexity that humans contain.

That's not a bug. It's a feature. Making use of that complexity makes us stronger and it brings benefits in everything we do.

Brian Carter, for example, is a highly successful speaker and marketing consultant. He's also a stand-up comedian who took two years of screenwriting courses to improve his creativity. It's easy to see how comedy skills might make him a more interesting keynote speaker -- and his speeches are always funny --but his business skills also enhance his comedy.

After each show, Brian would listen to a recording of his act and rate his jokes. He would measure how long the audience laughed and how loudly they laughed, and lay out his jokes in an Excel spreadsheet. He would use the sheet to calculate how many laughs per minute his act generated.

"I would create a level of efficiency from my set," he says.

By merging two very different interests, Brian is able to improve both of them.

But you don't even have to merge those different interests. Keeping them apart can make each highly effective too. After delivering a successful keynote filled with jokes and humor for a national company, the business asked Brian to create a webinar for its employees about Facebook marketing. That webinar was completely serious and explained how to use data to tell apart buyers, non-buyers and fans in ads and email marketing. It wasn't humorous but it was packed with practical techniques and useful insights. "They were blown away because they thought this guy was just funny," Brian recalls.

You could argue that even Brian Carter has a single goal. Ask him for his fifteen-second elevator speech, and he'll sum up himself up by saying that he likes to get results, and in practice he gets those results by poring over data sheets and Facebook stats. But he'll then use the remaining twelve seconds before the elevator doors open to explain that you shouldn't teach dogs to shake hands because they don't understand what they're agreeing to.

It's important to know why you're building your business. It's vital to focus, and it's crucial to know your strengths and your skills. But it's when you combine those strengths and skills and interests and all the paths that your curiosity takes you down that the magic really starts to happen. What is your Why is a single question about a single word. But it can -- and should -- have multiple answers.

Click here to listen to a full interview with Brian Carter on the FUN podcast.