So many of our modern rituals are tied to marriage and children. But what becomes of someone who doesn’t want either?

Deanna Zandt is a digital strategist with pink-streaked, short, spiky hair. Her Instagram feed is largely filled with pictures of her dog, Izzy. She is in an open relationship and doesn’t want children. Over her two decades of living in New York City, she’s collected a community of amazing friends and has stood witness with many of them as they got married or welcomed babies into the world. Despite not being a marriage person herself, let alone monogamous, she’s shown up to the weddings and baby showers and shed lots of genuine tears.

Now, she figured, it was her turn.

Ever since she saw the “Sex and the City” episode where Carrie Bradshaw questions why big parties should be only for getting married, she’d wanted to throw herself a wedding-size bash for her 40th birthday. So almost a year in advance of her big 4-0, she booked a beautiful rooftop venue in Brooklyn; found a caterer, a makeup artist and a photographer; set up a website; and sent out beautiful invitations. At a friend’s prompting, she even registered!

As you might imagine, the party planning confused a lot of people. “At every juncture,” Zandt says, some “people needed the explanation: ‘No, this [won’t be] a wedding. Yes, this is as ‘important’ as a wedding.’ But that was okay, because it gave me a chance to introduce people to a different way of thinking about what matters most.”

The invitations that Zandt sent out read: “This is not a drill. I am having a Fortieth birthday party this year which will serve as my non-wedding.”

With her friends, she didn’t have to explain much. “My tribe is super important to me, and they got it immediately,” she said. “I’m blessed to be in a milieu of people who value friendship as much as romantic and sexual relationships, so to them it was like, ‘Well, duh.’ ”

What her “tribe” may have been surprised by was that there was a ritual at the party by which Zandt, in a sense, married her community. Her friend Brianne Leslie, a clairvoyant with a thick Queens accent, said: “I love the idea for this party. You’re going to have a ceremony, right?”

“No, I think that’s taking it a little far,” Zandt had said, laughing. But Leslie cut her short: “No, stop right there. When people get married, it’s a public affirmation of their commitment. You need a ceremony that acknowledges the work you’ve put into creating this community and asks for their ongoing love and support.”

While Zandt had to admit it made sense, it still made her uncomfortable. She’d come to see ritual as something intimate: her daily meditation, the moments when she marked the new or full moon with a lit candle and an intention or two. “I think that’s part of why the ritual was squeamish for me, because I view it as very private, and this was so public,” she said.

Plus, she kept hearing this voice in her head, asking: Who do you think you are? Deanna is from a low-key, Lutheran family, and she appreciates the version of Christianity she grew up with. “It was lovely. You spent five minutes in the beginning saying, ‘Oh, we sinned. Sorry about that,’ and the next 50 was, ‘Yeah God! Let’s go get coffee.’

“I learned activism and community organizing from the church,” she continues. “My mom was really active, and my dad was a handyman. We’re German, that’s what you do: You help.” But you don’t necessarily throw blowout parties for yourself marrying 100 people on a Brooklyn rooftop. Even for someone who loves the spotlight, it felt like a stretch. “The public affirmation was the final piece that fell into place, and was a little bit squishy and scary.”

Another unexpected moment came the night before the big day. Zandt had made herself a skull-and-crossbones sash reading: Never the bride. When her mom, to whom she is super-close, read it, she stepped back. “Really, never?” she said, her eyes pleading.

Zandt was shocked. “Mom, we’ve talked about this. We’ve been having this conversation for 20 years. I’m probably not getting married and I’m definitely not having kids.”

“Probably?” her mom said.

“Unlikely, Mom.”

And here’s the thing about creating your own ritual: You force answers to potentially hot-button questions. Things that might have remained open questions —Will she ever get married? Will they christen that baby? — get resolved when you make up your own alternative. In some ways, that’s nice; it pushes people to own who they are. No more shape-shifting with conservative relatives. No more letting people hold out false hopes. In Zandt’s case, the open question of whether she may get married someday suddenly felt put to rest when her mother saw her in that skull-and-crossbones sash. It was hard, but honest.

And honest is what Deanna has decided 40 is all about. “Part of turning 40 is that you give way less of a f—,” she explains bluntly, then quickly laughs and adds: “Yes, there are some members of my extended family who might be totally freaked out by this whole thing. But I’m like, Aunt Helen, you do you; I’m going to do me.”

On the big day, Zandt, wearing a long, purple, sequined dress, stood beaming before her people as Leslie made it official: Today, Deanna is actually asking each of you, the members of her tribe, to enter into a commitment with her. In light of that, I would like you each to jointly take a vow with me. Do all of you promise to continue to love and support Deanna in her crazy and wonderful life and to laugh with her, celebrate with her, cry with her and be there for her when she needs your counsel, your compassion, or just your silence as you listen to her? If so, let us together say, “I will.”

And they did! Her family, her local tribe members, people who’d flown in from all over the country. (Zandt had arranged a fund by which friends with frequent-flier miles to spare could sponsor those who couldn’t swing a ticket.) Everyone was directed to wear “whatever makes you feel fabulous. Seriously. Show me who you are. PJs to gowns, faerie wings to T-shirts.” And they did: About 100 people showed up — in sequins and high-top sneakers and everything in between.

And just like a wedding, the evening flew by in a blur. Zandt closed down a nearby bar at 4 a.m. alongside those she loved most and felt most loved by in return.

This is an excerpt adapted from “The New Better Off: Reinventing the American Dream” by Courtney E. Martin, published by Seal Press.