Struggling to unwind? Why it feels like you’re always at work (even when you’re not).

Just as a smartphone can be a window onto the world, it can also be a backdoor into our personal lives, a way for clients and colleagues to reach us after we clock out. After-hours work emails tear at the tissue-thin barrier separating the home and office. The constant intrusion—or the threat of intrusion—can take a toll on our mental and emotional health. Because some part of us is always tethered to work, we can find it tough to completely unwind.

A 2016 study looked at more than 130 people who enjoyed two kinds of time off: time when they remained on call and time that was entirely their own. The study found that workers were more tired and agitated after a day on call than they were after a day to themselves. Workers also registered higher levels of cortisol, the primary hormone associated with stress. The finding held whether workers had to respond to a lot of work calls or just a few, suggesting the mere prospect of work can be just as draining as work itself. “The results demonstrate that non-work hours during which employees are required to remain available for work cannot be considered leisure time because employees’ control over their activities is constrained and their recovery from work is restricted,” the study noted.

If true, then many workers may never enjoy leisure time, as they are expected to read and respond to emails, or other work obligations, at all hours of the day. Technology only makes this problem worse. A 2011 study of college graduates found that smartphones and computers made the barrier between work and home more porous, particularly for employees who were expected to be available during their off hours. And a 2014 survey found that nearly half of office workers say the internet, email, and cell phones have increased the amount of time they spend working. Employers might be tempted to dismiss these intrusions, but they shouldn’t. Research shows that productivity declines after workers put in more than 50 hours in a week. They feel more stressed, sleep less, have more difficulty with focus, and more likely to make mistakes.

READ: Want to set better work boundaries? We've got tips.

Importantly, hours spent checking work emails—even while watching TV or taking the dog for a walk—are work hours. Every message from a colleague intrudes upon the precious time we enjoy with friends, family, and ourselves. For people who work particularly demanding jobs, it can be especially difficult to keep work from spilling over into other corners of life. But there are small things we can do to keep the tide at bay. “We have to be responsible for setting and enforcing the boundaries that we want in our life,” said author Nigel Marsh in his TED talk on work-life balance. “Being more balanced doesn't mean dramatic upheaval in your life. With the smallest investment in the right places, you can radically transform the quality of your relationships and the quality of your life.”

READ: Want to set better work boundaries? We've got 4 easy tips.

One solution is to refuse to check work emails during evenings or on weekends. (Earlier this year, France actually passed a law allowing employees to ignore work emails during their off hours.) If that’s not possible, try turning off notifications. Check in on work when convenient; avoid responding to emails at the drop of a hat. Or, set aside time that is totally work-free: dinner with family, drinks with a friend, or time for yourself to read, reflect, or meditate. “It's up to us as individuals to take control and responsibility for the type of lives that we want to lead,” Marsh said. “If you don't design your life, someone else will design it for you, and you may just not like their idea of balance.”