"But I have found that in the simple act of living with hope, and in the daily effort to have a positive impact in the world, the days I do have are made all the more meaningful and precious. And for that I am grateful."
Edwards's strength was first visible to the public in the way she coped with the death of her 16-year-old son, Wade, in a car accident in 1996.
"When Wade died, it was a terrible burden," she said on Larry King Live. "But it also reminded you both of the fact that you needed to grab hold of each day. You couldn't just take each day for granted."
Edwards told ABC News' Claire Shipman that her life stopped when Wade died.
"There isn't a parent who has lost a child in this country who doesn't know that," she said. "Everything exists before that time and then after that time."
The family friend said that Elizabeth wanted to communicate via Facebook because she feels a connection with so many people who have read her book and heard her speak. She wants to "exit with hope," the friend said, and in a way that she chooses.
Edwards' cancer, first diagnosed in 2004, went into remission but returned in 2007 while her husband was campaigning for the Democratic presidential nomination.
John Edwards said at the time, "Her cancer is back. We are very optimistic about this." Shortly after, Edwards' stage-four cancer was deemed incurable.
The couple appeared to survive John Edwards' admission that he had an affair with campaign aide Rielle Hunter, and Elizabeth even defended her husband against reports that he fathered Hunter's baby.
But the couple split after the former North Carolina senator finally admitted that he was the father of the baby.
Edwards would not comment on her marriage after he admitted he had fathered the baby, telling The Associated Press, "My marriage shouldn't be on anybody's radar screen except mine."
The couple, while formally separated, were seen grocery shopping together as recently as November.
Born Mary Elizabeth Anania, Elizabeth Edwards grew up in Virginia as the daughter of a Navy pilot.
She initially planned to teach literature, but ultimately pursued a law degree at the University of North Carolina, where she met John.
In recent years, Elizabeth authored two best-selling books and became a champion of causes involving poverty and cancer.
But always, she said, her children were her top priority.
"It scares me the most that there's going to be a day that, you know, is likely to come before I wanted it to come where I have to tell these sweet children goodbye," she said in a "Nightline" interview.
In her book "Resilience," Edwards wrote that she hopes to live long enough to see her three children graduate from school and hopefully have a grandchild.
"Eight years," she wrote. "That's all I ask for... I want to walk them to the door of the next part of their lives."
Edwards previously told ABCNews.com that her children will go to John and then, if he died, to Cate, a plan that she said was written into her will.
In her book, Edwards also pondered her legacy for her children.
"I do know that when they're older and telling their own children about their grandmother, they will be able to say that she stood in the storm...and when the wind did not blow her way and it surely has not, she adjusted her sails," Edwards wrote.