With so many of us working long hours to keep up with an ever-growing workload, and risking burnout just to keep up, the importance of rest is easily forgotten.

We avoid taking vacations and instead battle stress, illness, and the constant pressure to find time for all our commitments outside work.

But rest isn’t something to take lightly. It’s an essential part of doing your best work, being more productive at work, and is something more of us need to prioritize.

Why we don’t get enough rest

Americans are among the worst offenders when it comes to not resting enough. According to the Institute for Work and Families, fewer than half U.S. employees take all their vacation days.

And Project: Time Off, an initiative from the U.S. Travel Association, found Americans now take less vacation time than at any point in the past 40 years. And in 2014 Glassdoor reported that 61% of employees work during vacation.

We tend to think of vacation as an indulgence that we can’t afford, but as we’ll find out, it’s actually a necessary part of doing your best work.

Gary Oster, Managing Director of Project: Time Off, says “Many people don’t take time off because they think that it will negatively impact their manager’s perception of them. But, that isn’t the case at all.”

Employees also tend to worry about their work piling up while they’re gone, or being seen as replaceable. It’s also common for employees to believe only they can do their jobs, which takes away any option for vacation.

We don’t think we need to take time off

Beyond worrying about our workload, employees tend to be bad at recognizing the need for rest. This is partly because of our tendency, as humans, to focus on the short-term and our present selves over long-term benefits and what our future selves would want us to do now.

Though resting now by taking a vacation might be best for us in the long-term, we find it nigh-on impossible to ignore the short-term workload that’s piling up in front of us in order to take that break.

Katy Milkman, a behavioral scientist at the University of Pennsylvania, says that short-term high workload can also make it harder to make the right call for your future self. The more overworked and tired we are in the moment, she says, the more impulsive our choices will be—leading us to decide we just can’t afford a vacation.

Another reason Americans have so much trouble taking vacations is that it’s the cultural norm to work long hours and not take breaks. We all want to fit in at work, so if everyone else is working overtime and not taking vacations, we’re going to do that too.

According to David Dunning, a professor of psychology at the University of Michigan, work culture is quite different in Europe, where vacation and going home on time are encouraged. As a result, Europeans don’t feel guilty about vacation time the way Americans do.

If you spent some time in Europe, you’d think there are different ways to arrange civilization and work and family life. You’d get to see other choices are possible. A lot of Americans are stuck in the workplace overworking because that’s where everyone else is. That’s all you see. And unfortunately, in life, we’re channeled into who we are by what we don’t know is possible.

When Marilyn Kraut ran work-life programs in the U.S. to encourage more balance among employees, she said those who were adjusting their schedules were worried about the impression they were creating:

When people were trying to put balance in their lives, they kept it secret. They were afraid others would be jealous, or see them as lesser workers.

The combination of worrying about our work piling up or our jobs being taken away while we’re on vacation, and the constant reminders that our culture is built on work and not rest leave us overworked and exhausted. But it’s time we did something about that. Rest isn’t a luxury or an indulgence. It’s absolutely critical.

Why rest is so important

For me, not working is the real work. — Stephen King

Rest isn’t about being lazy or avoiding work. It’s necessary for our health and for being at our best when we are working.

Rest has been shown to improve cardiovascular health, and lower blood pressure and cortisol levels. Vacation in particular has also been shown to reduce the risk of heart disease, and increase lifespan.

A famous study known as the Framingham Heart Study followed roughly 12,000 men between the ages of 35 and 57, who were at risk of heart disease, for nine years. Using the data from this study, researcher Karen Matthews of the University of Pittsburgh Body-Mind Center found that the more frequently these men took vacations, the longer they lived. And these results remained true even after controlling for variables that are known to correlate to a longer lifespan, such as higher income and education.

When the Framingham data was explored by researchers at the State University of New York at Oswego, they found that men who took a vacation every year reduced their overall risk of death by about 20%, and specifically their risk of death from heart disease by up to 30%.

In another study of nearly 1,400 people, leisure time, including vacation, was found to encourage a more positive mindset and decrease levels of clinical depression. Research has also found women who don’t take time off are more likely to suffer from depression and, according to one study, 50% more likely to have a heart attack.

But beyond our health, there are other reasons rest is critical. From a business perspective, rest reduces the amount of sick days employees need. And with absenteeism costing over $3,000 per employee every year according to some estimates, it’s certainly something worth reducing.

Research also shows workplace performance improves after a period of rest and recovery, even among people who enjoy their work. And if you’re in a creative job, you’re going to need some rest in order to do your best work. A study from the University of York and the University of Florida found more than 40% of our creative ideas come during breaks and downtime, when our minds are free to wander.

Finally, you may actually be better off at work if you take more vacations. According to Project: Time Off, people who take all their vacation time are 6.5% more likely to get a promotion or raise than people who leave 11 or more paid vacation days leftover. While this is only a correlation, it’s worth taking note of. Especially if you’re a salaried employee with vacation time included—in that case, not taking your vacation time is much the same as volunteering for a pay cut.

While many of us feel guilty, uncomfortable, or nervous about taking time off, we can’t continue working overtime and de-prioritizing rest. It’s this constant go-go-go attitude that leads to burnout when our bodies just can’t go anymore.

Prioritizing rest and vacation time before you burn out is critical for doing your best work and living a healthy life.

I’ll leave planning your vacation up to you, but in the meantime, here are some tips for taking truly restful breaks throughout the workday.