Not even the most successful entrepreneurs get everything right in their 20s.
It would have three things on it, the 33-year-old said: a tennis ball, a circle and the number 30,000.
The tennis ball represents finding something you're truly passionate about.
"The most successful people and successful entrepreneurs I know are all obsessed with solving a problem that really matters to them," the MIT grad said. "I use the tennis ball for that idea because of my dog, who gets this crazy, obsessed look on her face when you throw the ball for her."
The circle reminds him to surround himself with the right people, he explained. "You're the average of your five closest friends, so make sure to put yourself in an environment that pulls the best out of you."
Finally, the number 30,000 comes from a memorable statistic he once stumbled upon, he told Bryant. "When I was 24, I came across this website that says most people live for about 30,000 days. So you have to make every day count."
Houston co-founded the file-hosting service Dropbox in 2007 with his MIT classmate Arash Ferdowsi when he was just 24. Forbes estimates he is now a billionaire.
He is not the first successful executive who would prioritize passion and the people around him if he could go back. When CNBC recently asked entrepreneurs about the advice they'd give their younger selves, chasing what you love and surrounding yourself with the best were common themes.