Venus Williams Says This Piece of Advice from Serena Changed Her Life

The tennis all-star and entrepreneur reveals one tip that Serena gave her that changed everything.

Venus Williams is best known as a tennis all-star and serial entrepreneur, but the greatest advice she has to offer has nothing to do with either of those careers.

"Are we talking work of life? Because my number one advice is don't date douchebags," she said yesterday during a Q&A with American Express executive Susan Sobbott at the SoHo branch of The Wing. Her all-female audience, sitting in millennial pink folding chairs at the buzzy, pastel women's workspace, erupted in laughter.

All jokes aside, said Williams, the best advice she's ever received was a more profound lesson—and it came from her younger sister, Serena.

"I definitely had one of my biggest failures down the street at the US Open in 1999," the 37-year-old Williams said. "Serena and I were both in the semi-finals in the US Open. We were kids ... and I asked her, 'So, Serena, are you nervous about tomorrow? And she's like, 'No, I'm not nervous because we have to show up. And since we have to show up, why not compete?' And that was the best advice I ever got in my life."

RELATED: Abbi Jacobson on Sex Toys, Broad City, and Bleeping Out Donald Trump

"Sadly, I didn't listen to it at the time," Williams added with a laugh, referring to the milestone match she lost to her sister. "That was one of my first biggest failures, and it was my biggest lesson, and my whole career changed after that ... You have to show up so why not compete? It's definitely the best advice, and it just never gets old."

Despite the expected competition, she considers Serena to be her fiercest defender. "We love each other, and we're extremely protective of each other," Williams said, adding that she felt those older-sister instincts kick in as a bridesmaid at Serena's recent wedding to Reddit co-founder Alexis Ohanian, when some day-of dramatics threatened to divert Serena's attention from her big moment. "That night I ran over to protect her too. I was like a mad dog. It just goes like that. We just love each other. We have the best time together."

Serena is not the only family member who offered Williams a career-making tip, she said. "My dad always said it's not about winning today. It's about winning tomorrow. You're building your game." Out of that grew the approach that Williams encourages at her activewear brand, EleVen. "EleVen is the philosophy of being better than a 10. Would you want to be the best or better? At EleVen we choose better because the best is stagnant. It's about always growing and never peaking. I never wanna peak."

VIDEO: Serena Williams Gets Emotional About Quitting Breastfeeding

On that note, Williams said, she has no plans to retire from her on-court career any time soon. But she has had to learn how to slow down, a "messy lesson" she internalized only after hitting a major professional road bump. Williams first launched EleVen in collaboration with the clothing store chain Steve & Barry's. The partnership ended abruptly when the retailer went bankrupt, and it was unclear whether Williams's fashion line would survive. "It was extremely stressful. It was hard to sleep," Williams said, opening up about the rough patch. But, she learned, "There are moments you have to create for yourself ... for your own sanity."

Her trick? "You know when Scarlett O'Hara [in Gone With the Wind] says 'I'll just think about it tomorrow?'" I swear I use that sometimes ... You have to stop. It's finding ways to get through that hard time but also knowing that there is that moment when you do get to stop."