Someone once asked Albert Einstein if he kept a notebook to record his great ideas.

“Ideas?” he said. “I’ve only ever had one.”

That one idea -- the Theory of Relativity -- marked Einstein as one of the greatest minds in history.

Not everyone will match him in terms of impact, but everyone can copy what he did. He found something that fascinated him and made it his life’s work.

Your interest, whether fashion, sports, science, music or whatever, can become expertise if you ask the right question and then search for the answer. Baseball stat guru Bill James is consumed by his life work.

“Even when I'm with my family, my mind tends to drift toward baseball,” he said.

Almost every human achievement comes from people who stay in a narrow field of work. Greatness is the product of specific study, not general interest. Marie Curie didn’t dabble. She threw herself into her research, at the cost of her life. 

Hall of Fame baseball player Rogers Hornsby was famously devoted his his sport, and to nothing else. When asked what he did during the winter, Hornsby replied, “I stare out the window and wait for spring.”

Einstein spent his life doing something else.

"I want to know God's thoughts,” he said. “The rest are details.”

So if you want to be a genius, don’t worry about intelligence. Think instead about diligence.

Mike Tully is author of "The Improvement Factor: How Winners Turn Practice into Success."