New York (CNN) -- South Carolina's first lady, Jenny Sanford, said Monday that writing her much-anticipated memoir of her husband's affair was a "cathartic" and "cleansing" experience.
In an interview on CNN's "Larry King Live," Sanford called "Staying True" -- which hit bookstores Friday -- "an honest account of the values I hold dear."
It was her husband Gov. Mark Sanford's loss of values that she blames on his much-publicized affair with an Argentine woman that was exposed by reporters after he disappeared for several days last summer. Staffers said he was hiking the Appalachian Trail, but he later admitted he was actually visiting his mistress in Argentina.
"It saddens me because I believed in him and a number of people believed in him," Jenny Sanford said Monday.
"I still believe he was a good person. ... Somewhere along the lines, he got off track," she said. "He can get back on track, but it's too late for the marriage."
Jenny Sanford, who filed for divorce in December, said the divorce could be final as early as the end of this month.
She said she found out about the affair in January 2009 when she discovered a letter her husband had written to his mistress.
"It was awful," she said. "I literally was in shock. My stomach felt gut-punched."
She said there had been warning signs, but she "never expected anything like this."
"I felt in some respects that we had lost something that we would never get back," even as she initially considered staying with him, she said.
"Nobody takes a 20-year marriage and decides in [a] snap minute to throw it away," she said. "I came to the decision very prayerfully and carefully over a number of months."
Sanford, 47, moved out of the governor's mansion with their four boys in June. She has said through the entire ordeal that her priority is her children.
"The kids are resilient, and we're back at home settling into a new, normal routine," she said of her sons, ages 11-17. "I feel like they're going to do great."
Asked whether she knows whether her husband is still seeing the Argentine woman, Jenny Sanford says she doesn't know and doesn't want to ask.
"I'm just moving on," she said. "I want to stay happy and positive and raise the kids to the best of my ability."