Sheryl Sandberg on dating after her husband's tragic death.

Sheryl Sandberg was happily married and kicking career goals as a best-selling author and Facebook chief, when, while holidaying in Mexico in May 2015, her world came crumbling down.

Her husband, SurveyMonkey CEO Dave Goldberg, died suddenly of a cardiac arrhythmia after collapsing at a hotel gym in Punta Mita.

The couple were away with Goldberg’s brother Rob and his wife – and the three of them were the ones to discover the 47-year-old lying in a pool of his own blood on the gym floor.

LISTEN: Sometimes, it’s beneficial to structure our grief. (Post continues after audio.)

“I started doing CPR,” Rob told TIME magazine.

“I remember not being sure if I could feel a pulse or if it was really my own heart pounding.”

Goldberg was rushed to a local hospital, where a doctor delivered the earth-shattering news to Sandberg that her husband had passed away.

A family friend also in Mexico, Phil Deutch, described the “awful, awful scene” that followed.

“The wails of her crying in that hospital were unlike anything that I’d ever heard in my life,” Deutch said.

Rob told TIME that he witnessed the moment Sandberg had to let go - both of her husband's physical body and to any hope he might wake up.

He recalled that as they were leaving Goldberg’s body, the 'Lean In' author ran back to give her husband one final hug.

"I think for Sheryl, letting go of him physically meant letting go of the moment that this could somehow not be real," he told TIME.

"I had to gently pull her off of him. She just wanted to hug him and wanted him to be there and wanted him to come back."

In her new book, 'Option B', Sheryl described the months of grief that followed that devastating day, comparing its effect on her life to a building being destroyed.

"It just kind of crumbled in every area. I didn’t think I could be a good friend. I didn’t feel like I could do my job."

"It reminded me of how one day in my neighbourhood I watched a house that had taken years to build get torn down in a matter of minutes. Boom. Flattened."

However, Sandberg slowly began to rebuild her life: releasing a new book designed to help others struggling with grief, and also starting dating again.

'Option B: Facing Adversity, Building Resilience, and Finding Joy' is a book she co-wrote with psychologist Adam Grant, which Sandberg describes as "our attempt to share what we’ve learned".

A post shared by Sheryl Sandberg (@sherylsandberg) on Mar 21, 2017 at 8:13am PDT

"A few weeks after my husband Dave died, I was talking to my friend Phil Deutch about a father-son activity that Dave was not here to do," she wrote on Instagram.

"We came up with a plan for someone to fill in so my son would not have to miss out. I cried, 'But I want Dave.' Phil put his arm around me and said, 'Option A is not available. So let’s just kick the shit out of Option B'."

"That became my mantra, and for the past two years I’ve tried hard to find meaning and happiness in the wake of our despair."

Part of Sandberg's journey to finding joy again has been to start dating - her current boyfriend is Bobby Kotick, who runs the gaming company, Activision Blizzard.

However, the mum-of-two knows as well as anyone who has lost a loved one that the feeling of missing them never really goes away.

"I feel it every day. Every day. I go to my son’s basketball game, and there are a lot of fathers there. My daughter is going to be in the school play next week, and Dave is not here to go to any of that."

Still, she's making the most of Option B.