It’s the holidays and yet most workers aren’t living it up.Difficulty unplugging from work, guilt about being out of the office and concerns about their reputation with their boss all factor into the worry many employees face about taking time off, according to a recent report.More than half of Americans had seven days of paid time off heading into the holiday season, according to the work-life balance survey by vacation and travel site Priceline.That’s more than most workers can, or will, use by Jan. 1, Priceline found. Further, more than 1 in 3 typically leave half of their days or more unused every year. Priceline polled more than 1,000 adults in October.While the vast majority of employees at least want to make the most of those hard-earned days off, Americans end up using only about half, or 54%, of their eligible vacation time, on average, according to a separate study by jobs and recruitment website Glassdoor.Only 23% of employees take all of the time they are entitled to — and 9% take no paid time off at all, Glassdoor found.Last year, American workers left a record 768 million days of vacation on the table, up nearly 10% from the year before, according to research from the U.S. Travel Association.”We are earning days faster than we are taking them, resulting in more unused days in total,” said Jamie Mageau, director of research at U.S. Travel.More from Personal Finance:Here’s where employers stand on 2019 bonuses10 rules for gift-giving this season4 ways to avoid the overspending trap this holidayOf the unused days, 236 million were forfeited completely, the equivalent to $65.5 billion in lost benefits. For each worker, that’s like giving back $571 in untapped paid time.”Those who plan their vacations for the year are much happier overall,” Mageau said.However, even as the end of the year approaches, it’s not too late to take a day here or there, said Liz Dente, Priceline’s chief people officer.”Your career is a marathon,” Dente said. “If you are not pacing yourself, you will burn out.”Subscribe to CNBC on YouTube.