"When you're young and you're successful and you're doing well and things are automatic for you in your life, you tend to think that that will continue for years on end," Sharapova tells CNBC Make It. "It's important to also be realistic about what can happen tomorrow. About injuries."
She would know: The tennis pro overcame a career-threatening shoulder injury in 2008 and then a 15-month doping ban after testing positive for meldonium, which was added to the list of banned substances at the start of 2016.
Sharapova used her time away from the Tour in 2016 productively: She enrolled in two Harvard Business School classes to develop her business skills and grow Sugarpova.
"I took a global management course and a leadership course," Sharapova tells CNBC Make It. The experience tested her time management skills, she says. "It almost felt like a job because you wake up really early, you study for something, then you go and take all the classes. ... And while I was doing that, I was still trying to stay in shape and work out, so by the time Friday came around and everyone's like, 'Oh, we're going out for happy hour,' I was like, I don't think I can handle this. I need to go take a nap."
But the most valuable lessons came from the people she met, she says. "I was surrounded by people that were older, wiser, that were much more accomplished in business than I personally was."