With the holidays quickly approaching, there's one gift most people forget to give themselves: a break.

In fact, 1 in 4 working Americans have nine or more days of paid time off remaining this year, according to a recent work-life balance report by vacation and travel website Priceline.

That's more than most workers can, or will, use by Jan. 1, Priceline found, which means many of those hard-earned days off will be left behind. Priceline polled more than 1,000 adults in October.

"Too often, people begin the year expecting to take full advantage of the vacation time they're given, but find themselves scrambling to use those days as December approaches," Priceline CEO Brett Keller said in a statement.

"Our advice is to treat your paid time off like any other work project," he said. "Plan ahead, keep track of the days available, and don't let the year end with that time unused."