A lot of people reach middle age having achieved some career success and ask themselves: Well, now what? Apparently this happens even if you’re Serena Williams.

Williams, who’s now 42, retired from competitive tennis a little under two years ago. She won 23 Grand Slam tournaments, more than any woman in the Open era and one shy of the record. Her level of fame and achievement — both on and off the court — broke boundaries for Black women and female athletes in general. She is, by most accounts, the best ever at what she did.

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Since retiring, Williams has directed that drive at new projects. She has a venture-capital fund, which mostly invests in founders who are women or people of color, and she just started a makeup line. She and her husband, the Reddit co-founder Alexis Ohanian, also have two small girls: Olympia, who is 6, and Adira, who will turn 1 this summer. So it’s not exactly like Williams has been idle. But the tennis court still calls.

She has gone back to it, in a way, with a new eight-part documentary called “In the Arena: Serena Williams,” which will stream next month on ESPN+. She told me that revisiting her career through the series has really been the first chance she has had to sit back and take in all she has accomplished.

One thing that I was thinking about while watching the documentary is really the kind of amazing competitive spirit that you had, and I’m curious about where that competitive spirit goes or how it changes once you’re no longer playing sports. You’re doing the different projects: the venture-capital fund, the makeup line, you’ve written a children’s book. Did you feel as if you had to find a new outlet for it? For me, it was a necessary thing. I needed to not be done and sit down and wake up and be like: “Oh, my God. What just happened?” It was definitely too fast to throw myself full-heart, full-body into everything, but that’s kind of what I needed to do to survive after I’ve been playing tennis all my life.