(CNN) Nearly two years ago, Facebook executive Sheryl Sandberg received a new role -- one no one would sign up for: widow.

Now she's trying to help people who have experienced a loss around the grieving with her new book "Option B."

"Going through this ... it's the unimaginable. Those early days ... months, weeks, I felt like there was this void closing in on me. The grief. I couldn't breathe. And I didn't know what to do. I turned to my friend Adam and I said, 'How do I get my kids through this?' Because I was so worried their childhoods were going to be wiped away," Sandberg told CNN's "The Lead with Jake Tapper" on Tuesday.

Sandberg said if her book can help anyone who is also facing a hardship, "It honors the life [Dave] led. And like so many people who have lost someone, I want his memory to stay alive."

Dave Goldberg was just 47 when he passed away while the couple was on vacation in Mexico. The tech entrepreneur had been exercising when he fell. An autopsy later revealed the cause of his death was a coronary arrhythmia, a symptom of his undiagnosed coronary artery disease.

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