'You're Not Old Until You Act Old': Mark Cuban's Advice on How to Stay Entrepreneurial Even When Considering Retiring The "Shark Tank" star and entrepreneur is worth an estimated $5 billion.

Mark Cuban has always been vocal about his humble beginnings and his struggle with being "broke" before his career as an entrepreneur and investor took off.

In a new interview with GQ, Cuban talked about how important luck and timing were to his success, and how he's redefined what retirement means to him — and why he never plans to fully get there.

Mark Cuban on luck and timing:

Cuban told the outlet about the struggle that came before starting his software company, MicroSolutons.

Related: Mark Cuban's Grocery Store Hack Will Help You Score Cheaper Produce

"I was broke, like, on my a** life broke, I was terrified. I was having fun, I enjoyed my life. But you're not two, three years out of college, sleeping on the floor, just having gotten fired, and thinking, 'This is exactly the way I planned it,'" Cuban said. "I always tell people life is half random. And that's just a reality for everybody. I got lucky … You gotta have timing. I was really lucky in that."

Cuban later sold MicroSolutions for $6 million at age 32 before joining his friend as a partner for Broadcast.com, which sold in 1999 to Yahoo for $6 billion.

"I was a tech guy who understood networking when the internet stock market blew up," he told GQ. "And I was an entrepreneur who was willing to invest his own money to try to take this new thing called the internet and see if we could put audio and then video over it."

On budgeting:

Cuban told the outlet he still keeps a tight budget to this day, something he learned from the early days of selling his first company when he had around $2.5 million in his bank account.

The billionaire explained that there's a "huge difference" in being a millionaire and a billionaire, even going from $10 million or $25 million.

"I went back to Dallas, but I was trading stocks. I was starting to make a lot of money trading stocks," Cuban recalled of the time right after selling MicroSolutions. "But even then, I didn't feel like, 'Okay, whatever I want, I can be extravagant.' Same house, same everything, same car ... It wasn't when I was a billionaire on paper because that was just on paper. It really was when I was able to monetize it."

Related: Mark Cuban Doesn't Have a Butler and Does His Own Laundry. 'I Try To Be The Same Person As I Was When I Was Poor.'

On retirement:

Cuban says he plans to keep buying, selling, and investing in companies — until he gets bored.

He said retiring means picking "exactly what you want to do," and while for many that may mean relaxing and exiting the corporate world, to Cuban, it just means shifting gears. Cuban said taking time to party and fly around the world early on in his career made him realize that he was "bored just having fun."

"You're not old until you act old. Being able to compete just keeps the juices going, keeps my mind sharp," Cuban said. "I remember when I was the youngest kid walking in and trying to sell to people three times my age. Now I'm on the other side of the spectrum. I'm competing with kids a third of my age, and I love it."

Cuban is a star of "Shark Tank," owner of the NBA's Dallas Mavericks and healthcare company Cost Plus Drugs (among other entrepreneurial pursuits), and has an estimated net worth of $6.55 billion, per Bloomberg.