Like many entrepreneurs, Maria Sharapova's new full-time job started out as a side hustle.

In February, the five-time Grand Slam singles winner retired from professional tennis and immediately poured herself into Sugarpova, the high-end candy company she co-founded in 2012. The move was years in the making--inspired, she said on Wednesday at the Inc. 5000 Vision Conference, by the competitive drive she developed over the course of her stellar athletic career: "I said I would love to own something 100 percent, where I create my own team, I bring in the right resources, the finances, and I make the decisions every single day."

When Sharapova, 33, first launched Sugarpova, she had no idea what she was getting herself into. "You never really grasp the attention to detail, the focus that you have to create, when you're in the midst of beginning and continuing to have your own business," she said.

For help becoming an effective CEO, she drew lessons from her athletic career. The financial acumen came from her experience negotiating endorsement deals with companies like Nike and Motorola. Her ability to lead a team, she said, came directly from her years of working through high-pressure situations with coaches, trainers, and support staff--and learning to prioritize balanced schedules and frequent off-days to avoid burnout.

Now, Sharapova uses similar strategies: For example, after realizing that she was tuning out after an hour of daily meetings, she created a self-imposed limit of two or three calls per day. Continuing to work after losing your focus is "incredibly taxing on yourself, on your mind, on your body, and then you're just playing catch-up," she said. "Don't overdo it. I know that's one of those suggestions that seems so difficult in today's environment, but having that time for yourself will only make you a better leader."

Sharapova has also become an avid startup investor, and even made a guest-judge appearance on Shark Tank--a longtime favorite show of hers--shortly after her retirement. Her advice to founders looking for funding: Pitch your company as authentically as possible. "I quite like when the founders are slightly nervous," she said. "I think that's when their vulnerability shines through, and seeing how they come out of that and how they challenge themselves ... really shows what they're made of."

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