He celebrated by buying a lifetime unlimited AAirpass from American Airlines, a ticket to fly wherever, whenever, and retired from business to see the world, he tells The New York Times. But it didn't last long — he was soon back at it, working on his internet company Broadcast.com, which sold to Yahoo for $5.7 billion in 1999.
So how does Cuban stay motivated to do more after such huge success? Cuban, 59, says one thing has been key: The endless pursuit of knowledge.
As a young person, Cuban would stay up late reading computer manuals and business books.
"A guy with little computer background could compete with far more experienced guys, just because I put in the time to learn all I could," Cuban writes on his blog. "I read every book and magazine I could. Heck, $3 for a magazine, $20 for a book. One good idea that led to a customer or solution and it paid for itself many times over."
Now worth $3.7 billion according to Forbes, Cuban is still learning. Last summer, he read four non-fiction books on topics ranging from machine learning to foreign affairs: 'The True Believer: Thoughts on the Nature of Mass Movements,' by Eric Hoffer; 'Machine Learning for Dummies,' by John Paul Mueller and Luca Massaron; 'The White Working Class: Overcoming Class Cluelessness in America,' by Joan Williams; and 'Mr. Putin: Operative in the Kremlin,' by Fiona Hill and Clifford G. Gaddy. He also took a Python computer programming class on his phone.
"I'm trying to keep up with what's happening around the world," Cuban told Politico of the summertime workload.
Between investing on ABC's "Shark Tank," overseeing the Dallas Mavericks NBA team (which has had some recent controversy) and raising three kids, Cuban has a full plate. So why spend time on books and classes?
Cuban says maintaining an information advantage is the only way to be competitive and succeed.
"Particularly in the tech industry, the only constant is change," Cuban explains during an interview on "The Jamie Weinstein Show" podcast. "So you've got to stay up, because otherwise, there is some 12- or 18-year-old kid that is coming in with a better idea to kick your a--."
So to succeed in business, "do your homework and know your business better than anyone," Cuban says on his blog.
That desire to stay ahead keeps Cuban going: "I'm always afraid of failing," he writes. "It's great motivation to work harder."
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Disclosure: CNBC owns the exclusive off-network cable rights to "Shark Tank."