Sheryl Sandberg has been remarkably open about what's it's like to unexpectedly lose the love of your life and the father of your children.

Since her husband Dave Goldberg collapsed and died while the couple were on holiday together in May 2015, Sandberg has spoken regularly about the grieving process, and how she's handling it.

Now, she's shared an insight into how she's helping her two children get through it as well.

The key? Resilience.

In a recent op-ed for The New York Times Sandberg says breaking the news of Goldberg's death to their two kids was the hardest thing she's ever done.

"Flying home to tell my 7-year-old daughter and 10-year-old son that their father had died was the worst experience of my life," she writes.

"During that unimaginable trip, I turned for advice to a friend who counsels grieving children. She said that the most important thing was to tell my kids over and over how much I loved them and that they were not alone.

"In the fog of those early and brutal weeks and months, I tried to use the guidance she had given me. My biggest fear was that my children's happiness would be destroyed by our devastating loss. I needed to know what, if anything, I could do to get them through this."

Sandberg says the best advice she received was to build their resilience; to make sure that when bad or disappointing things happen to them, they have the emotional tools to overcome it.

"As parents, we sometimes feel helpless because it’s impossible to solve our children’s problems. In those situations, we can still provide support by ''—walking alongside them and listening," she writes.

And the resilience kids learn to lean on when bad things happen can also help them deal with grief.

"One afternoon, I sat down with my kids to write out 'family rules' to remind us of the coping mechanisms we would need. We wrote together that it's okay to be sad and to take a break from any activity to cry. It's okay to be happy and laugh. It's okay to be angry and jealous of friends and cousins who still have fathers. It's okay to say to anyone that we do not want to talk about it now. And it's always okay to ask for help.

The poster we made that day—with the rules written by my kids in colored markers—still hangs in our hall so we can look at it every day. It reminds us that our feelings matter and that we are not alone."

Sandberg says she also made videos of her children talking about their memories of their father, so that in the future they could watch them and know that what they remembered about him was real.

And, of course, Sandberg makes sure to remind them herself, whenever she sees a little bit of Goldberg shining through.

"My hope is to hold on to Dave as he really was: loving, generous, brilliant, funny and also pretty clumsy. He would spill things constantly yet was always somehow shocked when he did.

"Now, when emotions are running high in our house, but my son stays calm, I tell him, 'You are just like your daddy.' When my daughter stands up for a classmate who is getting picked on, I say, 'Just like your daddy.' And when either of them knocks a glass over, I say it, too."

H/t: The New York Times