"I'd have more confidence in my preparation than I did then," he said. Bottom line: Cuban didn't have the pedigree, the suit, or the car—but what he lacked in polish, he made up for in hustle.

Bottom line: Cuban didn't have the pedigree, the suit, or the car—but what he lacked in polish, he made up for in hustle. And if he could give his 20-something self advice? Stop trying to impress ...