In 2001, during the summer before his junior year of high school, LeBron James attended a basketball camp.

One of the speakers was Kobe Bryant. Then just 22 years old, Kobe was already a two-time All-Star and NBA champion. He had already, for want of a better way to put it, "figured out" how to reach the highest level of his profession, where he would remain for over a decade.

Years later, what did LeBron remember most? Not Kobe's tips on technique. Or training. Or persistence, effort, and embracing a relentless drive for excellence.

According to Matt Sullivan's Can't Knock the Hustle, this is what Kobe said that stuck with LeBron:

Don't rely on basketball for your happiness, because it's not gonna happen.

Make sure you balance your life out, you have something there for yourself in life, so when the game is over, you know exactly what you want to do.

In large part, Kobe was talking about life after basketball. Maybe a camper's playing days would end after high school. Or college. Or, for a few, after a professional career. 

But the end would come; as the scout tells Billy Beane in Moneyball, "We're all told at some point in time that we can no longer play the children's game. ... Some of us are told at eighteen, some of us are told at forty, but we're all told."

But "the end" also comes at the end of every workday. At some point, no matter how driven, we all put down our devices and computers and our pursuit of professional excellence and achievement.

Which means, at some point in the day, business can't make us happy. Work can't make us feel fulfilled. A sense of professional purpose, no matter how compelling and gratifying, can only extend so far.

In those moments, you need something that is yours. Something that doesn't depend on professional success. That can't quantified by revenue, or market penetration, or user growth. 

Something, as Kobe said, that is "for yourself in life," whether at the end of a particular entrepreneurial or professional journey or at the end of a long workday.

Because business can, at times, be fulfilling and rewarding. And can even make you rich.

But it can't make you happy. Not over the long term.

So take it from Kobe, and make sure you have something there for yourself: Not just at the end of the journey, but each and every day.