There's a reason Americans are known for being workaholics. It's estimated that 40% of U.S. employees work more than 50 hours per week, while 20% put in 60 hours or more.

Given the effort many of us sink into our careers, you'd think we'd feel entitled to a reward in the form of a much-deserved vacation. But in reality, Americans treat themselves to a ridiculously small amount of time off.

In a 2014 survey from Skift, a travel website, 42% of Americans admitted to not having taken a single day of vacation. Not surprisingly, lower earners were the most likely to avoid taking time off.

But it's not just low-income individuals -- presumably, those least likely to get paid time off in the first place -- who aren't snagging a break. A 2016 Bankrate study found that more than half of Americans across all income ranges forgo a portion of their paid vacation days each year.

Not only does giving up vacation days essentially equate to leaving unclaimed money on the table, but it also puts you at serious risk of a major career zapper: burnout.

And while it's a buzzword many of us are used to hearing, there's actually a real medical definition behind the term. According to the Mayo Clinic, burnout is categorized as "a state of physical, emotional, or mental exhaustion combined with doubts about your competence and the value of your work."

And that sounds pretty serious. Worse yet, in a 2015 study, more than 50% of employees felt they were experiencing job-related burnout, and while there are other factors that can no doubt contribute to this unfortunate phenomenon, not getting a much-needed break is a big one.

If you've fallen into the trap of giving up some, or all, of your vacation days, it's time to rethink that habit. Otherwise, you could actually end up putting your career at risk.

Why aren't we taking vacation?

It's one thing not to take vacation because you haven't earned any paid time off and can't afford to lose a portion of your income. But passing up the vacation days you're entitled to is a whole different story.

According to Glassdoor, there are several reasons why Americans give up vacation time, including:

Fear of falling behind on work obligations

Not having a backup available to handle key tasks in their absence

A general inability to disconnect

Of course, these are just some of the reasons to avoid taking vacation, but another big one is general job insecurity. Because most U.S. companies have an "at-will" employment policy, they can fire employees for any reason, provided they're not violating a specific contract, labor union agreement, or discrimination law. As a result, many workers feel that if they take vacation, and things don't fall apart in their absence, their companies will view them as less valuable and terminate their employment.

Then there's the notion of coming home to a mountain of work that's enough to keep countless employees chained to their desks. Think about it: If taking a week off means spending the next three weeks working till all hours of the night to catch up, it erodes the value of that vacation and virtually eliminates its appeal.

Finally, employees who are vying for a promotion or raise might also shy away from vacation for fear of falling out of management's good graces -- even if that fear is completely unfounded.

You need a break

If you're among the innumerable Americans who avoid taking vacations for fear of the consequences involved, you should know that you may be harming not just your career but your overall health.

Rather than forgo those earned days off, think about the reasons why you're so hesitant to escape and come up with a game plan to address them.

Imagine you've avoided a vacation thus far for fear of falling behind on deadlines. If you map out a plan of attack in advance, and put in extra time in the weeks leading up to your vacation, you'll be better positioned to escape with a clear head. Of course, in an ideal world, you wouldn't have to do this, and there'd be someone else in your company available to help pick up the slack. But in the absence of that, if you put in additional time before you go away, you'll be less stressed knowing that most of your work has already gotten done.

Similarly, if you're worried that an emergency situation at work might arise in your absence, you can designate a colleague to handle unplanned fire drills while you're away. Then, when that person decides he or she needs a break, you can return the favor.

Finally, realize that while taking a vacation might seem like the sort of thing that could put your job at risk, if you perform well consistently and constantly make an effort to bring value to your company, you're less likely to lose your position over a week's escape in the middle of the year.

Sure, your team might grumble while you're away, but if anything, the fact that you're missed while on vacation is a good sign, as it means you're obviously relied upon to get things done.

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It's easy enough to go without vacation time and uphold the routine of plugging away at the office. But if you don't grant yourself a break eventually, you risk reaching the point where you lose energy and motivation -- and that could compromise your job more so than any modest vacation will.