Kobe Bryant says the key to success is something anyone can do

Kobe Bryant secured five NBA championships before retiring last year after 20 successful seasons with the Los Angeles Lakers.

The basketball legend is looking for success in a different arena now: investing.

He and his partner Jeff Stibel — who have already invested in 15 businesses together since 2013 — recently unveiled a $100 million venture capital fund, which they'll use to invest in technology, media and data companies.

While the success of their newly established firm, Bryant Stibel, has yet to be determined, it will all boil down to one thing, Bryant told CNBC : "Our mantra is value growth. To grow, you have to constantly learn, you have to constantly move, constantly improve. That's the key. That's what makes life fun."

It's one of the reasons he doesn't hesitate to reach out to, and learn from, other successful people. "What I love doing is cold-calling people, getting their book list," he said. "'What did you read? What did you learn? How did you learn it?' Those are the questions."

Bryant isn't the only successful person who feels strongly about adopting a growth mindset.

Self-made billionaire Richard Branson, for example, says he still hasn't "made it." Like many of the world's highest achievers, who continually push themselves out of their comfort zones and look for ways to self-educate, Branson doesn't want to get complacent.

"The way I see it, life is all about striving and growing," Branson wrote on LinkedIn. "I never want to have made it; I want to continue making it!"