Facebook COO Sheryl Sandberg says a phone call with Mark Zuckerberg after her husband's death changed her leadership style

After her husband Dave Goldberg died unexpectedly in 2015, Facebook COO Sheryl Sandberg was suddenly a single mom with one of the biggest jobs in tech.

Sandberg sought the insight of grief counselors, who told her that she should return to the office 10 days after her husband's death, to see if her work would serve as a welcome distraction.

She dropped off her kids at school and lasted about four hours at Facebook. "As far as I could tell, it was a total disaster," Sandberg told media mogul Oprah Winfrey for an upcoming episode of Winfrey's "Super Soul Sunday." The OWN network shared a preview clip with Business Insider.

Sandberg said that she had trouble focusing, rambled, and even fell asleep in an executive meeting. That night she called Facebook CEO Mark Zuckerberg to tell him, "Maybe it's too soon. I made a total fool of myself."

He replied with, "Lots of people sleep in meetings!" she told Winfrey. He then added, "But I think you made a really important point today," and noted what it was. He told her that she can choose to return whenever she was ready, but that he wanted to let her know that she helped the team even during her difficult first day back.

"It was the nicest thing anyone could have done," she said.

Sandberg would later see this phone call as a teaching moment. Sandberg eventually compelled Facebook to double its bereavement leave period to up to 20 days, but she told Winfrey that she also knows the importance of small gestures. She tells employees going through a difficult time that they can resume their full responsibilities when they are able to, but that she still thinks they're the best person for the job, and is quick to point out when they do good work.

Drawing from her own experience with Zuckerberg, Sandberg finds that this little assurance doesn't come across as an imposition on a vulnerable person, but rather a comforting reassurance that they are still a valued member of the team and not an outsider marked by tragedy.

"I think people have a lot to learn from the example Mark set," Sandberg said in an interview with Business Insider's US editor in chief Alyson Shontell in May. "To be honest, I don't know how he knew this. I didn't know this. He did a bunch of stuff that I certainly never thought to do for people I worked with who were grieving. It's a pretty incredible story."

You can see Sandberg's full "Super Soul Sunday" interview on OWN on June 25.