Here's The Huge Mistake 42% Of US Employees Make

Flickr / andy_cThe beach is calling your name.

It's simple math: the more time you spend at work, the more productive you are. Right?

Well, maybe not.

Taking time off actually makes employees more productive, according to a 2014 study by Oxford Economics. "Paid time off leads to productivity gains as workers report returning to work refreshed and with a better attitude," it says.

And yet, 42% of Americans only used part of their vacation time in 2013, leaving an average of three days on the table, the study reported.

Nearly 40% of employees feel so buried under their workload that they can't justify taking time off, and another 13% are too intimated by the work that will pile up while they're gone.

While logging extra hours at work may seem like the only solution to tackle an ever-growing to-do list, in reality it could be hurting your overall productivity. Taking a break gives you time to rest, both mentally and physically, and return with a clear head and renewed energy for old projects.

Buda Mendes/Getty ImagesPerhaps an adventure-filled vacation is more your style.

Even before leaving for vacation, employees see gains in productivity as they rush to meet deadlines and work ahead to make up for the time they'll be away, the study reports. This makes sense - no one wants to return to a huge pile of assignments, so your motivation to get as much done as possible before leaving hits a high.

Other research also supports taking advantage of your vacation days. In 2006, Ernst & Young found that for every additional 10 hours of vacation time an employee took, their performance ratings improved by 8%, reported the New York Times.

Similarly, a Cornell University study revealed that employees at insurance company New Century Global who took consistent breaks performed 13% more accurately than those who worked straight through, according to The Atlantic.

Vacations offer benefits other than increased productivity. They leave us with better attitudes at work, enhance our physical and mental health, and improve our social lives, according to the Oxford Economics study.

Taking vacations also staves off burnout, which can leave you perpetually exhausted, angry, unable to concentrate, and even depressed. If you take time off to relax, take a mental break from the stress of work, and spend time with loved ones, it gives your brain a chance to recharge before heading into another anxiety-filled week.

So don't let your extra vacation days go to waste - even simply tacking an extra day onto your weekend could be the difference between high-performing and burnt out.