Alison Stevens hasn't taken a real break in 18 months. She says this over the phone during what's supposed to be the first day of a week-long family vacation. First, she has to take our interview, and then she has a few meetings to wrap up with her team. Then Stevens, 51, who admits she's "terrible" at taking time off, will try to unplug while reading a book on the beaches of Cape Cod — as long as there's no cellphone service to distract her.

As the director of HR services at Paychex, a payroll services company, Stevens leads a team of over 600 HR professionals who support small businesses.

The pandemic has caused a nonstop deluge of work. The burnout many people are feeling well into 2021 — at work and in life — is especially acute for some in human resources.

"Part of the stress is that, by nature, HR professionals tend to take care of others before themselves," Stevens tells CNBC Make It. "It's how we're hardwired."

"That, combined with the fact that the pandemic isn't over," she adds.

With health experts saying we're as a whole closer to the beginning to the pandemic than the end, there's a real need for workers leading through change to brace for more challenges ahead. Employers agree that providing mental health resources is important, but some HR workers say there's simply too much work to be able to fully step away and prioritize their wellbeing.

'The volume is what's killing us'

According to a recent Paychex Pulse of HR Report, which surveyed 1,000 HR decision-makers in the U.S., 98% of HR leaders say the pandemic has transformed their role; 70% say this has been one of the most challenging years of their career.

Since March 2020, armies of HR workers have been key to helping companies shift to remote work. They've been tasked with laying off tens of millions of workers, then trying to hire them back during a global health crisis. They've conducted survey after survey, drafted every type of business update and filtered down messages from the top, oftentimes bearing the brunt of negative feedback from employees.

Stevens describes her work in the last 18 months as "a roller coaster."

Noelle, 35, has always said that working in HR can be a lonely experience. She works for a large health-care organization in New York City and asked we not publish her full name so she could speak freely about her work.

Her employer was in the crosshairs of being in a Covid-19 hotspot early in the pandemic, while also suffering from revenue shortages from halted elective procedures. She and her team of seven were in charge of processing some 300 layoffs, or 10% of her organization, from April through October 2020 — "that's not even counting the furloughs," she says, of which she's lost track.

Of course, mass cuts mean more work for the people who remain, who then turn to HR for support in managing it all. The cuts have made too much work for too few people, Noelle says: "The volume is what's killing us."

Her organization is so short-staffed that she's had to deny some time-off requests. It also means that Noelle herself has barely taken any time off recently. Leaders encourage people to make time and space to step away, she says, but it's nearly impossible in practice.

"Our staffing is in such critical shape that we can't allow people to take time off even if they need it," she says. "Just as I'm sure it's the case for any other professional or manager, if you take days off, the stuff just piles up."

Acting as the messenger

The Paychex report found nearly eight in 10 HR leaders say they are a strategic partner within their company and continue to be involved in C-suite conversations about new business initiatives.

But that doesn't make it easy for HR workers to be the messengers between employees on the ground struggling through the health crisis, and leaders at the top making decisions about how, where and when people work.

"Sometimes the people at the top feel strongly about things, but my role is to execute on them regardless of how I feel," Noelle says. "Resisting the need to respond about how you feel is a personal challenge."

Noelle says she's spent much of the last year consoling people who must report onsite for work but have concerns about contracting the virus. She recalls one person who said being called to work during Covid was an all-but-certain death sentence. "It's hard to know the right reaction to these types of statements," Noelle says.

Stevens says HR has a responsibility to normalize conversations around burnout and anxiety so employees feel comfortable sharing what they're feeling. But it's also up to senior leaders to "get down to level of employees themselves, and have conversations with employees to make sure we're really checking in."

Hiring and mental health support

The state of the job market, where people are quitting in droves and employers can't fill new openings, makes hiring the biggest challenge for HR workers competing in today's "talent wars," Stevens says.

The competition puts more pressure on HR to make sure their organization is offering the best and most attractive benefits, including competitive pay; flexible work arrangements; ample health and wellbeing support; and sufficient pandemic resources to attract workers.

Good mental health benefits are key to recruiting, HR leaders say, as well as retaining employees.

Internally, an overwhelming majority — 96% — of HR leaders believe employee mental health is an employer responsibility, according to the Paychex survey. Roughly half say the No. 1 change they're making to support employee mental health is promoting awareness of resources, but Stevens says that's only part of the equation.

Tapping mental health benefits must be encouraged, modeled by senior leaders, and easily accessible. Leaders may want to make sure HR workers are taking their own advice.

"Now, HR professionals really need to lean into taking care of themselves," Stevens says. "They need to make sure they're taking advantage of the benefits they're working to shape for their employees. The benefits they've built are more important than ever as we go into the next couple of months in particular."

Return to office isn't a return to normal

In the spring, as vaccination efforts improved and Covid cases leveled off, a return to offices by the fall seemed all but certain. The highly contagious delta variant has changed all that, with the CDC reinstating their indoor masking guidance, more workplaces requiring vaccinations and some companies pushing their return plans to 2022.

Whenever the next leadership decision is made, HR will be there to shepherd workers through it, facing employee criticism and all.

Stevens tries not to take it personally. "Every day we're hearing news that tells us the pandemic is not over, and our anxiety remains very high. So our response to things like return-to-office continue to be quite heightened."

But she's realistic that a return-to-office plan isn't a return to normal. Taking the long view could help overworked HR professionals remember that what comes next is a marathon, not a sprint.

"Those strategic changes can't be made in weeks or months," Stevens says. "We're experiencing a big shift in the way work gets done, and it will take several years for HR and business leaders to understand how we operate and best support our employees."

Check out:

U.S. workers are among the most stressed in the world, new Gallup report finds

1 in 3 people say return-to-office negatively impacted their mental health

'I'd rather bet on myself': Workers are quitting their jobs to put themselves first

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