Serena Williams became a professional tennis player at the age of 14, and for more than two decades she has consistently trained and followed a healthy diet to help her win 23 Grand Slam titles.

But besides her strenuous workout routine and vegan diet, Williams, 38, says she has two non-negotiable strategies — whether she’s training for a tennis match or not — to help her stay productive while also juggling motherhood and multiple business ventures.

“Something I do every day is [to] completely turn my brain off, which sounds weird but because I work so much between tennis and running my other properties—Serena Ventures and Serena Clothing. But it’s a lot so I just need to turn my brain off and not think about anything,” Williams tells CNBC Make It.

Williams says she finds little ways zone out, no matter what’s on her schedule.

“Sometimes it’s mediation. Sometimes it’s watching a program [on TV] that has nothing to do with anything, like something that is silly or fun,” Williams says.

Williams says having her 2-year-old daughter, Alexis Olympia Ohanian Jr., also helps when it comes to clearing her mind.

“It’s a lot easier now because I can just watch my baby,” Williams says. “It really helps me to focus on her and focus on the moment and not think about anything else. And I purposely do that with her because I know that I just need to shut off.”

AUCKLAND, NEW ZEALAND – JANUARY 12: Alexis Olympia, daughter of Serena Williams and husband Alexis Ohanian look on during final match between Serena Williams of USA and Jessica Pegula of USA at ASB Tennis Centre on January 12, 2020 in Auckland, New Zealand. (Photo by Hannah Peters/Getty Images)

Giving her brain a rest allows Williams to “reset and get more energized to go train the next day or take more work calls,” she says.

In addition to clearing her mind, Williams also drinks at least a gallon of water a day, even outside of training. “That is one thing that I make sure that I always do,” Williams says. (Dehydration can make you feel tired or sluggish. Water intake varies, especially for active people like Williams, but Harvard kidney specialist Dr. Julian Seifter recommends four-to-six cups a day for most healthy individuals.)

Wiliams’ tennis star sister Venus, 39, told CNBC Make It in October that her go-to tricks for peak performance include getting eight hours of sleep and laying off junk food like her favorite pancakes and honey buns.

This article first appeared on CNBC and is republished with its permission.