“We just didn’t know how to quarantine back then,” said Shannon Tremaine, who lives in Brooklyn, of the first time she had to spend weeks by herself.

That was back in February, after her boyfriend at the time tested positive for Covid-19. The rule then, before vaccines were widely available, was no contact with the outside world for two weeks, and it was emotionally painful.

“I literally spiraled,” said Ms. Tremaine, who is 29 and works for a financial crime intelligence firm. “I would wake up and say, ‘OK, I have a thousand more hours of this.’”

Fast forward to this month as she undergoes another period of isolation, after contracting the virus at a holiday party. Following Centers for Disease Control and Prevention guidance, she is alone for 10 days, but her experience this time has been much more positive.

(It’s also worth noting that the C.D.C. uses the term “quarantine” for “when you may have been exposed to the virus and may or may not have been infected,” whereas isolation is “when you have been infected with the virus, even if you don’t have symptoms,” though people tend to use them interchangeably in conversation.)

Even with the body aches, sweats, fever and cough, the symptoms seem more manageable, and come without the anxiety she felt the first time around. “Last time I didn’t know what was going to happen to me or how bad it would get,” she said. Now that she’s vaccinated, she feels fairly confident that she will “have a few days of flu symptoms, and then will be fine.”

One of the vital lessons she learned when her boyfriend had Covid was the importance of reaching out to other people in self-isolation — not a hard task since multiple friends tested positive after attending the same holiday party.

“We are all going to find a topic we are passionate about in the world and do a five- to 10-minute presentation on Zoom,” she said. “We are also making a calendar for our friend who is turning 30: Everyone has to do a sexy photo shoot at home.”

And — perhaps most important — she now knows to look at the positive side of having all this time to herself, even though she’s under the weather. “I am going to take some time to just sleep, which I haven’t been able to do in a long time,” she said.

The Omicron variant is ravaging the country, having just surpassed Delta as the most common variant in new cases. It is infecting some people who already had Covid and forcing them into isolation once again.

Of course, some of the ill are so sick that they have no choice but to spend the 10 days consumed with battling the virus. But those with mild or no symptoms are applying lessons they learned the first time to make this period of self-isolation more productive, peaceful and benign.

David Schavone, who is 43 and lives in Los Angeles, said that, unlike his first period of isolation in March 2020, he knows to use this down time wisely.

“Being sick and being able to say, ‘Sorry, I’m canceling all my meetings,’” said Mr. Schavone, one of the owners of RedThumb Natural Wine. “I’ve been doing end-of-the-year tax stuff and prepping for next year — the stuff that always gets pushed aside for meetings and sales.”

“This first time around I was really scared the whole time,” he said. “This time I am trying to be productive. I actually think I am being more productive than I would be if I wasn’t sick.”

Other people getting Covid again are also more effectively managing their anxiety.

“The big difference between last time and this time is I’m not worried I’m going to die,” said Lauren Sfayer, 35, who lives in Brooklyn and works as a medical sales representative for a genetic testing company.

She had Covid a year ago and couldn’t stop her mind from going to dark places, thinking about all the people she had heard about who had died, she said. “I was so anxious, I was chugging NyQuil so I could sleep through it. I was just too stressed.”

She tested positive for Covid again last week and is in another period of self-isolation. But this time, she reminds herself that she is vaccinated and her body has successfully battled this virus in the past.

“This time I can actually watch television,” she said. “I’ve been watching ‘Sex and the City’ from the beginning.”

She also learned the importance of making her apartment hospitable. “Last time I lived in filth,” she said. “When I tested positive last week I was like, ‘I’m going to be here for a while.’ I cleaned up my apartment, changed my sheets and put on fresh pajamas.”

When he contracted the virus in March 2020, Luis Lizarazo, 37, a talent manager, had to self-isolate with his husband in their small one-bedroom apartment on the Upper West Side. When they recovered, they decided to move to an apartment with two rooms in case they had to go through that again.

“I always felt that we needed to prepare for the worst,” he said. “We moved to a different part of the Upper West Side where we could get a two bedroom for not much more than we were already paying.”

That decision paid off in November when they both contracted the virus again. “This quarantine was a lot more pleasant,” Mr. Lizarazo said. “I had my own space with all my drag stuff and my books and records.”

Then there are those determined not to form bad habits during periods of self-isolation. They learned that structuring their day is essential.

Charles Williams, 24, a recent college graduate who also owns a T-shirt design business in Kansas City, Mo., got Covid for the first time in March 2020. He had to isolate in his dorm room and was so bored he would let himself sleep for hours on end. “It really messed up my sleep schedule even after I was out of quarantine.”

He has tested positive for Covid again and is now doing his second period of self-isolation. To avoid the mistakes of the past he is forcing himself to wake up early every day and have some semblance of a schedule. “I try to get up and do a little stretching and working out, maybe some push-ups and situps,” he said. “It is making me feel better even if I spend the rest of the day watching TV or playing video games.”

“I’m not getting stuck or losing track of time now,” he said. “I think it’s going to make things easier once I get back into the real world.”

The need for structure is even greater if you have kids, said Tania Swain, 42, a widow with two special needs sons, ages 10 and 8, who lives in Makanda, Ill. All three of them are currently staying home for the third time in six months as a result of Covid exposures.

“I’ve learned that setting up a schedule helps a lot,” said Ms. Swain. “I say to them, ‘We are going to get through breakfast, clean up, and then you can have a reward. Or we are going to unpack our groceries, put them away, and then you can have freedom. If you let them do whatever they want all day long, you are going to get nothing accomplished.”

She’s also discovered the need to be an even more present, compassionate mother.

“Kids are going through this transition also, and they hear a lot of scary things about Covid. They can even be afraid someone is going to die,” she said. “I’ve had to really be present for them and talk to them.”

Another trick she’s learned: give her sons something to look forward to every day whether it’s a present or a drive to their favorite park or extra screen time. “You have to know what motivates your children,” she added. “They need something special right now.”

Treats aren’t just for kids. Mr. Schavone tried to be healthy and practical during his first period of self-isolation in March 2020.

This time, he abandoned self-discipline. When ordering his groceries, he asked himself, “‘What do I really want?’” The answer was chicken nuggets and some bottles of wine, he said, “for when I started to feel better.”