Christmas was always her father’s holiday. Courtney Arnold’s dad loved the music. He loved the tree. The two of them would sit side-by-side on the floor, sorting through strands of brightly colored lights to make sure every bulb was glowing.

Her father hadn’t yet been diagnosed with cancer on their last Christmas together in 2014, but Arnold had noticed that he looked thinner and seemed weaker. After the holiday, when she helped him carry the tree out to the curb, she spontaneously snipped a sprig of pine from the branches. Somehow, she knew she needed to keep something tangible from that moment.

She’s been thinking about all of this lately, as the seasons shift and a torrent of memories comes rushing back.

“It’s starting to get to the holidays,” she said, as she sat in a cozy living room on a recent evening, surrounded by a circle of women she knew would understand. “And Christmas lights, I mean. I can’t do it. My father was the light man. Like you could see my house from outer space.”

The Georgetown apartment filled with laughter.

Arnold was 24 years old and preparing to start law school at American University when her father died of lung cancer in 2015. The grief overwhelmed her. She tried group therapy but found she was often the youngest person in the room — sometimes by many years. Then she saw a post on Instagram about the Dinner Party, a national nonprofit group that supports young adults who have suffered a significant loss by bringing them together over potluck dinners.

The organization began eight years ago in Los Angeles, when co-founders Lennon Flowers and Carla Fernandez — who had both lost a parent to cancer — threw a casual dinner party for friends who had also experienced parental loss. Word spread, and people started asking how to organize similar dinners themselves.

The Dinner Party has since grown into a national community led by more than 250 hosts across the country, as thousands of young people have been drawn to its intimate settings, created to help them mourn and heal. It is a refuge that offers particular comfort to the bereaved around the holidays, when festive parties are filled with superficial chatter and social media feeds are flooded with idyllic Instagrams.

On this crisp November evening, a group of a dozen women filled paper plates with roasted acorn squash, pot pie and corn bread, before settling into chairs and meditation pillows in the home of 26-year-old host Sarah Tralins. Passing bottles of wine, they chatted about how they were really doing, and who they were missing — mothers, fathers, friends, siblings — with the arrival of a season steeped in nostalgia.

“I had a panic attack in Target that first year, and I was like, well, I learned my lesson! No going to Target between the end of November until after Christmas,” Arnold said, shaking her head. “It’s three years now, and I still have these blocks.”

For Tiffany Virgin, 26, Thanksgiving is harder than Christmas.

“I get very ugh about Thanksgiving because it’s very much a family holiday,” she said. “My dad used to make the turkey, he used to make the pie. My mom doesn’t cook so my dad did all of it. I’ve downplayed it a lot, I make it not such a big deal, but secretly it is a very big deal to me. I just don’t allow myself to get very excited about it, knowing the absence of him.”

Samantha Garko, 30, who lost her stepfather three years ago, started nodding. “I downplay Thanksgiving a lot, too,” she said. “For the longest time, Thanksgiving was just me and my mother and my stepdad, just the three of us. So when that goes down to just me and my mom, it’s very noticeable.”

The gathering felt more like a friendly hangout than a structured group therapy session, which was exactly the point. While dinner hosts like Tralins are given training and support by the Dinner Party, they are not professional grief counselors, and the goal of the organization is simply to offer communal support to young people who are trying to learn how to live well after loss. And for the people in Tralins’s living room — whether they were still moving through a raw grief or had lived many years since the death of their loved one — the group had become a particularly vital resource.

“I’m really grateful for this space,” Virgin said. “It’s like therapy, but even better because everyone understands.”

“You don’t get that look,” said Katherine-McClain Tuite, 24, who lost a friend in an accident several years ago.

“You can also drink,” Ally McKay, 27, whose father died of cancer, said with a laugh.

The group shared certain commonalities: None had children. All were still navigating the self-discovery of their 20s and early 30s, and so they talked a lot about their sense of identity — how they had changed as time carried them further from who they were when their loved ones died.

“I’ve been struggling with the idea that my sister didn’t know me as the person that I currently am,” said Zara Tillem, a 27-year-old architect whose younger sister died six years ago. “I’ve exceeded her knowledge of me, and that’s kind of difficult to work through.”

Madison Chase, 24, said she often thought about what life was like before her mother’s ovarian cancer diagnosis, and has struggled to fully comprehend the end of that era: “I still have dreams where she’s healthy, and alive, just out there still somewhere.”

Arnold, who was preparing to graduate with a double degree, explained that her father had last known her as a prospective grad student, so moving on from that stage of life felt emotionally fraught.

“My father died a couple of months before I started law school; I was doing my tour of American, and he was dying in bed,” Arnold said. “For me, my entire law school experience was directly related to my father’s death. It’s all tied up together.”

Tralins compared the abrupt transition to the turning of a page: “I almost view it as a chapter,” she said. “Chapter one was with my dad.”

Her father died suddenly in an accident when she was 12, “and it’s been very hard to reconcile, because there was this whole other existence, a whole other trajectory with this other person,” she said. “So the readjustment to the second chapter — from the chapter with to the chapter without — it’s been really hard for me.”

Each of them had stories about making that adjustment, and the decisions they made about what to keep — belongings, traditions, fragments of memories — and what to let go.

Heather Rameau, 27, took up her late father’s habit of sending loving notes to her mother, diligently putting a card in the mail every couple of weeks.

Virgin insisted on sorting through her father’s things right away, fearful that they would otherwise sit untouched for far too long; but she saved his last voice-mail message for years.

They spoke about the weight of symbolic dates, the ache of holidays and anniversaries and birthdays. But grief doesn’t abide by logic or a calendar, and they talked about that, too — how the presence or absence of sorrow could feel equally shocking.

“Sometimes,” said Garko, speaking about the anniversary of her stepfather’s death, “you survive the day and you realize you’re actually okay.”

“But then it comes for you two days later,” added Lauren Archambeault, 24.

As a veteran host, Tralins knew that the intensity of the group’s conversation could continue to reverberate in the days after their dinner. So as the clock ticked past 9 p.m., she gently steered the discussion toward the transition from the comfort of the room to the reality of the world waiting outside.

“It can sometimes be very hard to go back into the week,” she said. “So let’s take a few more deep breaths.” The room fell silent, save for the sound of exhalations and Tralins’s soft voice. “Ask yourself, what can you do for yourself this week?”

Arnold knew her answer. She thought of her father, who would not be there to see her graduate. She thought of what the group had talked about, the need to make room for both before and after, with and without.

“I’m going to order my regalia for graduation,” she said, and her friends cheered. “It’s time.”

A new chapter lay ahead. But always, hanging on the wall of her apartment, she kept a special shadow box holding a small, fragile branch of her father’s last Christmas tree.

An earlier version of this story erroneously stated that all of the women gathered at Sarah Tralins’s home were unmarried. The story has been corrected.