‘The Let Them Theory’ started as self-help. Now it’s a whole lifestyle.

In 2018, it was “Girl, Wash Your Face,” with Rachel Hollis as the Bible-quoting sorority Big you never had — or, as she dubbed herself, “Tony Robbins for women.”

Today’s credo: “Let Them,” touted by inspirational speaker Mel Robbins — first on her podcast and social media accounts, and now physically circulating in her massively popular book. “The Let Them Theory” has grown thick as kudzu over the culture, its green cover — in a shade midway between Brat summer and a Girl Scout sash — practically vibrating off the shelf. Sales in 2025 alone have put Robbins in the league of such publishing powerhouses as the Obamas, E.L. James and Randy Pausch — “exclusive company and quite an accomplishment,” Brenna Connor, an industry analyst at market research firm Circana, said in an email to The Washington Post.

Robbins’s previous book, “The High 5 Habit,” was also a commercial hit. It advocated giving yourself a high five in the mirror each morning and sold more than 200,000 copies. But the success of her latest “is a whole different scale, by far,” said Reid Tracy, chief executive at Hay House Publishing. “Just in English alone, we’ve sold 3.6 million.”

Tracy pointed to a few factors that may have helped “Let Them” break out. Robbins had an enormous audience on her podcast, at times beating Joe Rogan on the Apple and Spotify charts. She was also a guest on countless other podcasts — including an early episode of Oprah’s — and promoted the book tirelessly. (Robbins’s publicist declined requests for an interview due to her busy schedule.)

“I’ve been working at Hay House for 37 years, and we’ve had lots of big-selling books, but nothing as big as this,” Tracy said. “It just has a life of its own, it’s a once-in-a-lifetime book, and you know — no one can ever tell you why it became so big.”

The “Let Them” theory, such as it is, is simple: Release what you can’t control — namely, the opinions, emotions and reactions of others — and reclaim your time and energy. The book spells out this magic phrase at length, explaining how to apply it in various situations: to friendships; to strangers you meet at the park or in the grocery checkout line; to people in your life who might be struggling. Robbins bulks up the front half of the book with promises of how, should you choose to embrace it, this worldview will change your life; the back half contains a grab-bag of life tips, such as, “Compliment people everywhere you go” and “Give your bedroom a small makeover.”

The central insight isn’t new, as Robbins herself says. It pops up in all sorts of places and guises: Buddhist teaching, Stoic philosophy, the Serenity Prayer. (Nor is this wording particularly new: Some have criticized Robbins for not crediting Cassie Phillips, whose poem “Let Them” went viral in 2022; Phillips told the New York Post that she got it from a Tyler Perry movie, after a snippet of dialogue by his character Madea became a trending sound on TikTok.)

Why has that message landed so powerfully right now? Though books about “inner work” and “personal growth” have generally enjoyed strong sales in recent years, according to Shannon DeVito, director of books at Barnes & Noble, the popularity of “Let Them” might be a reaction to the pandemic. Thanks to Zoom, she said, “You know so much about your family and the people you work with.” Now readers want help creating a sense of personal space and inner peace.

Robbins with a copy of “The Let Them Theory” in the studios of her production company in April.

“For anyone who lived through covid, you started to see where your friends and family maybe have divergent political views — mask views, vaccine views,” said Ann Turner, a therapist based in Washington. “We’ve had to figure out how to live amongst people who are different than you — this theory, I think, is very helpful for that.”

The book, published just before Christmas 2024, also arrived on the heels of the election, during a period of intense polarization, acute news fatigue and all-around societal malaise. As technology has made us excruciatingly, inescapably hyperconscious of the lifestyle, habits and passing thoughts of those around us, Robbins’s advice provides a coping mechanism. If hell is other people, “let them” seems to offer a path to salvation.

For many, “Let Them” hits closer to home. At a bookstore discussion that Turner led this spring, aimed at women in midlife, several participants connected Robbins’s message to the stresses they felt from years of helicopter and snowplow parenting. “Let Them,” Turner observed, “resonates a lot with moms who try to manage everything.”

Emily Howe, a small-business owner who has run a months-long “Let Them” book club, said she felt seen by Robbins’s tell-it-like-it-is candor. “She talks about, ‘life is stressful,’” said Howe, quoting one of the early chapters. “I think for a lot of years of my life, I denied that.” Over the phone, her voice thickened slightly as she recalled how moved she was by the family anecdotes in the book, especially Robbins’s emphasis on what her daughter Sawyer, a co-author of the book, taught her about relinquishing control. “I’m tearing up because I have my own daughter, and I learned so much from her,” Howe said.

“Lean In” launched a thousand op-eds, but “Let Them” has lodged deep in readers’ psyches. The Facebook group for “Let Them” tattoos has nearly 17,000 members, many of them women in their 50s and 60s getting their first ink. They book their appointments alongside their friends, sisters and daughters; they ask for tips about how to find the right artists. They get “Let Them” written in their mother’s handwriting, or surrounded by flowers or birds. In my text exchanges with one member, she seemed to work through the “Let Them” mindset with almost alarming velocity — at first asking to remain anonymous to keep her husband from finding out, then deciding it was unlikely he would ever read the story, then declaring that, either way, “I don’t care anymore.”

Shantell Rock shows off her tattoo inspired by “The Let Them Theory.”

Shantell Rock, a paralegal in Virginia, got “Let Them” tattooed on her forearm after getting hooked on the audiobook, which she says she’s listened to hundreds of times. “As a mother, as a former wife, as a human being — we really like control,” she said, adding that the phrase “really released me mentally.”

But for Rock, the sometimes forgotten other half of Robbins’s message — the phrase “Let me,” a recommitment to what is within the reader’s power to change — has been equally important. It’s been especially helpful in her community advocacy, including with groups such as Moms Demand Action, during challenging times. “Let those crazy people do what they’re going to do,” Rock tells herself. “And then let me do what I need to do, because I still need to fight for the less fortunate. I still have to do my part.”

After posting a photo on social media, Rock learned that, unbeknownst to her, her cousin LaWan Raddler, in Louisiana, had also gotten a “Let Them” tattoo — in Raddler’s case, on her hand.

LaWan Raddler's tattoo is a physical reminder in everyday situations.

“I read the book, and I knew instantly that this tattoo was meant for me,” said Raddler, whom Rock conferenced in on our call one weekend morning. “I have two kids, and I’m a single mom. Sometimes these kids will make decisions or do things, and you just have to constantly remind yourself, just let them. Let them grow, let them learn, and sit back and just be a goddess — and that’s all you can do.”

“That’s what I said!” Rock chimed in.

Raddler needed that physical reminder in everyday situations, she added. “It could be something very minor — like you could be in the car, and somebody cuts you off, and your hand is on that steering wheel,” Raddler laughed, “and I promise you: You will look at that tattoo.”

Maybe that’s the magic of the mantra, delivered just when the dominant national mood seems to be a kind of road rage: It feels like Mel Robbins herself putting a friendly, restraining hand on your shoulder. It can be hitched onto every conceivable human interaction. In the office: Let your co-worker act a little short in that meeting. The next time you’re on an airplane? Let your seatmate cough. On the dating apps: Let them ghost. Perhaps its allure lies in how little it seems to ask of us. It can sound steely or easygoing, imperiously above-it-all (“let them eat cake”) or like a casual brush-off (“let them have their fun”).

If it still seems a little contradictory that people can feel so passionate about cultivated indifference, so fervent about being laissez-faire — that a nation of busybodies and rubberneckers is telling itself, through gritted teeth, “not my circus, not my monkeys” — well, the proper response (perhaps the only response) is staring us right in the face. There it is, in boldface type, on the cover of the book. Two simple words. Do I even have to say them out loud?