There is a distinct line between working hard and burning out. Managers want highly engaged, energetic employees—but often it is those employees, the hardest workers, who, after a few months of running hard on a project hit become deflated or quit.

One in five highly engaged employees is at risk of burnout. Worker burnout occurs when an employee’s high work performance and efforts take a toll on their mental and physical health. How do you retain and continue to attract these high-performing employees and keep them from burning out?

Give them what they need to do their job

No one can stay on a treadmill too long without fatigue, and if its broken, injury. Hardworking employees will become frustrated and exhausted if they are exerting themselves and not moving anywhere. Poorly functioning or nonexistent resources, like reliable updated software, highspeed printers, and highspeed internet, can force employees to work twice as hard to get their work done. Similarly, high levels of bureaucracy and lack of autonomy slows progress no matter how hard someone works. Added paperwork and reporting to a micromanager is added time diverts time and energy away from the work they are passionate about and engaged in and the results these high-performers thirst for. To prevent exhaustion, it’s important to pay attention to what could be stealing away a worker’s energy. Give employees opportunities to let management what resources they need and what barriers are getting in their way.

Have backups

Giving employees generous vacation and sick time is worthless if they can’t break away without their projects collapsing or a massive workload piling up. Make sure for every role in a project, there is at least one other designated back up that can fill that role in at any time. This has the added bonus of giving employees more varied experiences and training. When people are sick or they are faced with a personal life emergency, that needs their full attention. Their work will suffer and so will they if they try to work through it. Personal time keeps employees happy, healthy, and balanced. Returning to projects after a break can bring a whole new perspective and energy.

Allow flexible environments

Those who are prone to burnout tend to be self-motivated and responsible—they will get their work done, so anything that makes it less stressful and helps with work-life balance should be promoted. This can mean allowing people to telework, adjust their work hours, have walking meetings, and take courses or go to events that will build their skills or network.

Acknowledge work and give feedback

One common cause of burnout is a perpetual feeling of inadequacy. Highly engaged workers may question their results and feel they are struggling at or below mediocre if managers never acknowledge or reward their efforts. This will make them push harder and harder. It’s important for managers to give feedback to all employees but don’t overlook those who are doing well. It doesn’t mean you need to give superficial praise but show an interest in what they are doing.

Don’t burn yourself out

One of the most stressful experiences is working for someone who is stressed out. Additionally, managers set the example. Employees who see their managers working around the clock may feel pressured to do the same. Watch for signs in yourself as well as employees. Invite your employees out to lunch sometimes—showing its okay to take a break. Do not email or call your employees after hours unless it is urgent.

While they may be the top performers in your company, they are suffering from stress often accompanied by depression, sleeplessness, and poor self-care—and they are much more likely to leave. High turnover is not good for a manager for many reasons. What’s more, smart and savvy job candidates will steer clear of any place with a reputation of high turnover.