A three-week trip to Guatemala last year should have been the ultimate opportunity for Brett Mathiowetz to unwind. Instead, the construction company owner was stressed out, with work on his mind.

“It was a bittersweet kind of deal,” he said. “Whenever I take time off, it’s hard not to feel like I’m just abandoning the company and my responsibilities.”

So this year, he didn’t take any time off. Like many American workers, Mathiowetz is approaching year’s end with several vacation days still unused. He’s faced with the same conundrum as other vacation hoarders: “Do I take half a week off when things are busy just to try to use it up,” he wondered, “or do I lose it?”

As 2014 comes to a close, workers with vacation days still in the bank are finding themselves struggling to make a withdrawal — even as paid time off is becoming more flexible and people are able to stay plugged in while away.

Workers hang onto vacation for many reasons. Some save their days for a big trip or extended time off at the end of the year. But a more common trend, research shows, is the feeling that they just can’t leave.

“We push ourselves really hard as a country to work,” said Amy Falink, a former human resources professional and a senior lecturer at the University of Minnesota Carlson School of Management. “A lot of that is cultural.”

What’s worse is that vacation time here is so limited. The United States is one of the only advanced economies not to mandate paid vacation for workers. While the average American worker gets 10 days of vacation per year, France, by comparison, requires every worker to get at least 30. Nearly 25 percent of American workers don’t receive any paid time off at all, not even holidays.

So why, when paid time off is so preciously limited, do Americans leave unused vacation days on the table each year?

Some workers get signals from their supervisors that a break would be unwelcome. The No. 1 reason people say they don’t use their vacation time is that their “work schedule does not allow for it,” according to a recent survey from travel booking site Expedia.

“This data seems to say more about employees’ bosses than employees themselves,” said Expedia spokeswoman Sarah Gavin.

But much of the time, the decision to skip out on vacation is self-imposed — a psychological legacy, perhaps, of the economic recession.

“You’re afraid of missing out, of stepping away, that somehow that’s going to weaken your position,” said Anne Weisberg, senior vice president of the Families & Work Institute, a research group. “You’re afraid to take a break, even when taking a break makes you more productive.”

That fear includes what might happen when one returns from vacation, namely the deluge of e-mails and other backlogged work that await people’s return.

Peer pressure to work

Mathiowetz tried to stay plugged in in Guatemala, where he went with his family to learn Spanish. He even Skyped meetings with his company in Sleepy Eye, Minn. But he still worried that he was “losing touch with the flow of things.”

He also admitted that he was concerned about appearances. He said that as an owner, he worries what his employees think of him when he does take time off.

Peer pressure, which tethers people to their desks, is real, said Nancy Lyons, president and CEO of Minneapolis media firm Clockwork. Clockwork is one of a growing number of companies without a formal vacation policy, and Lyons has gained national notice for her practice of granting employees as much vacation time as they want.

The company previously offered a set number of vacation days, but “it just became sort of silly, like baby-sitting,” she said.

The new plan has its own difficulties, however. Critics of so-called unlimited vacation policies complain that the policy fosters distrust among colleagues, and that without an official number of days in the bank, employees feel subtle pressure not to take time off.

“Leadership can adopt this stuff, but if the person next to you thinks you’re a slacker because you’re actually doing it, that’s a problem,” Lyons said.

But Angie Doerr, director of technical operations at Clockwork, said vacation time shakes out similarly to how it would at other companies, with newer employees taking less time than office veterans. She averages two to three weeks off per year, but last year when her grandmother died, she was able to take an extended break to grieve.

“You only question it if people miss whatever they were accountable for,” she said.

Take time, be productive

On the opposite end of the spectrum from Clockwork are the majority of companies — fully 84 percent — with “use-it-or-lose-it” vacation policies, according to a study by the U.S. Travel Association. In those workplaces, people who don’t take their allotted time off end up working for free.

Those policies “can sound almost threatening,” said Katie Denis, senior director at the U.S. Travel Association, which, naturally, promotes worker breaks. But the policies ultimately benefit workers, she said, because they create deadlines that spur workers to use their time.

Mary Frey, a receptionist, said she used to hoard her vacation every year in case she needed to tend to her parents, who were ill. Now, her parents are gone, and it wasn’t until checking her end-of-the-year balance that she realized that she was due a break.

The only challenge: She can’t decide how to use it.

Mathiowetz said that by hoarding his time off over the years, he has forfeited weeks of vacation that could have been spent on the beach, in the mountains or even just at home. His company is in the process of adopting a new policy that allows employees to carry some of their time over from year to year.

Workers and business stand to benefit; time off has been documented to reduce stress and increase productivity.

“That hoarder mentality — we’re really trying to break that down,” said Denis, of the U.S. Travel Association, “because ultimately what you’re sacrificing in the process is so much more valuable than leaving 10 days in your leave bank.”