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 sought the insight of grief counselors, who told her she should return to the office 10 days afterward 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 the media mogul Oprah Winfrey for an upcoming episode of Winfrey's "SuperSoul Sunday." The Oprah Winfrey Network shared a preview clip with Business Insider.

Sandberg said 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."

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

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

Sandberg later saw this phone call as a teaching moment. She eventually compelled Facebook to double its bereavement-leave period, to up to 20 days, but she told Winfrey she also knew 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. She's also quick to point out when they do good work.

Drawing from her experience with Zuckerberg, Sandberg said she found that this little assurance didn't come across as an imposition on a vulnerable person, but as 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 "SuperSoul Sunday" interview on OWN on June 25 at 11 a.m. ET.