When Yasmene Mumby was 27, the stress of her job reached a devastating peak: She developed a blood clot behind her left eye, making her lose half of her vision for a year.

Mumby was a Harvard-trained educational policy and leadership expert, who worked her way up from teacher to national director of organizing partnerships and strategy at the nonprofit Leadership for Educational Equity.

"It was such an overwhelmingly rewarding role that also was overwhelmingly burning me out," Mumby, now a 36-year-old management and strategy consultant in Brooklyn, New York, tells CNBC Make It. " I was moving in my purpose, but also still working seven hours, seven days a week. Sometimes, when we got in the thick of it, 12-hour-plus days."

Mumby says she loved the work, but it took a huge toll on her mental and physical health. She also grew a large uterine fibroid, and later found a lump in her breast.

"My body made me take a moment to pause," she says.

It's unclear whether Mumby's job strain was the sole cause of her health complications. But there's a direct link between women's stressful work lives and health, largely due to the body's inability to differentiate between "life-threatening stress" and "ongoing stress," studies show.

And 88% of Black women professionals say they've experienced burnout during their careers, according to research from consulting firm Every Level Leadership.

The experience forced Mumby into the "slow life," choosing "well-being over working myself to the bone," she says. Unexpectedly, she became a higher achiever — simultaneously running her consulting firm The Ringgold and serving as director of communications for the Advanced Education Research & Development Fund.

She does that while still prioritizing family, yoga and the outdoors, and making more money than she used to, she adds.

It sounds improbable. Slowing down allowed Mumby to work more efficiently, she says: "My approach to living in a way that honors my well-being and creates an environment for my family, my newborn son, to thrive means that I'm dedicated to intentional thinking and consistent action."

That includes promoting mental and physical health, not taking on time-sensitive projects, avoiding extra workloads and being vocal when her limits are being pushed.

It's easier said than done, Mumby adds: Some workplaces don't have this outlook. You can look for these three work-life balance red flags before taking a job offer, a group of leadership coaches told CNBC Make It last year:

1. The company doesn't train its managers to identify and mitigate burnout
2. The company expects you to be available before or after working hours
3. The company praises employees for working beyond their necessary hours

"In some places, in some conversations, people devalue that choice. And it's not seen as an elevation or evolution professionally. It's seen as a devolution," says Mumby. "I don't ascribe to that mindset."

DON'T MISS: Want to be smarter and more successful with your money, work & life? Sign up for our new newsletter!

Get CNBC's free report, 11 Ways to Tell if We're in a Recession, where Kelly Evans reviews the top indicators that a recession is coming or has already begun.