(CNN) -- It's doubtful there's ever a perfect time or place to end a marriage, but for Dean McDermott, that time and place was in a Palm Springs, California, hotel room after playing a round of golf.
Mary Jo Eustace said she's been able to take her 2006 divorce from Dean McDermott and turn it into a positive.
The actor told his then-wife, Mary Jo Eustace, that he'd been having an affair with Tori Spelling and that he'd found his soul mate, Eustace recalled Tuesday on HLN's "The Joy Behar Show."
"[He said], 'I'm leaving you -- she loves me unconditionally,' " Eustace said.
Eustace replied that "you've known her [for] three weeks. I actually thought it was a joke. I thought I was being punked. But it was true," she told Behar.
Eustace offers life lessons she learned from the 2006 split with McDermott in her book "Divorce Sucks: What to Do When Irreconcilable Differences, Lawyers Fees, and Your Ex Husband's Hollywood Wife Makes You Miserable," which arrived in bookstores Monday. Watch Eustace describe her shock »
Donald Trump's ex-wife Marla Maples; Dina Matos, ex-wife of former New Jersey Gov. Jim McGreevey; and Lance Armstrong's ex, Kristen, also appeared on Behar's show to break down what happens during and after very public breakups.
When Eustace found out her 13-year marriage was ending, she said she was "in a really ugly bikini -- missing like padding on one side, holding my daughter in my arms," but at least the bomb wasn't dropped in front of news cameras.
Matos was standing right next to her husband when he admitted at a press conference that he'd had an affair with another man.
"I was in shock because I had only learned three days before that he had been involved in a relationship," Matos recalled on Tuesday's show. "I was there in the moment. I was there physically but mentally, you know; I was just trying to maintain my composure and not fall apart in front of the cameras."
When a marriage ends, "you think this is the end of your life as you know it," Matos said. "And in some ways it is. You feel powerless."
Especially once the media picks up on the crumbling matrimony. "The first week that my divorce was announced ... I saw a picture of my ex-husband with his new wife's legs wrapped around his head," Eustace said. "You're in complete survival mode."
Although Lance Armstrong's post-marriage flame, Sheryl Crow, wasn't the reason his five-year marriage to Kristen ended, she told Behar it was still difficult to watch. And yet the hardest part for Kristen Armstrong was disliking her former husband's new love.
"I really wanted to dislike her," Armstrong said. "I really did. [But] she's beautiful. She's smart. She's funny. She was great with the kids. For as much as I wanted to dislike her and I tried, I couldn't."
Matos said it's different when your husband leaves for another man. "When your husband leaves you for another woman, at some point you know there was love in the marriage, and you had something," she said on Tuesday's show.
"But when your husband is not the person that you think he is, you know, he's an impostor -- then you start questioning every aspect of your life together. What was real? Did he ever love me? Why did he marry me? Later I found out why," she said.
After McGreevey announced his affair, Matos said she found papers that appeared to be the outline for a book that said McGreevey married her "for political gain," she said. "He married me because he wanted to become governor and perhaps president. That's very painful."
All of the ex-wives said they've been able to use their divorces as a time to grow. "You feel dehumanized, horrible," Eustace said of divorce.
"With lawyers and fighting and feeling unloved and unlovable, and the media thrown into it, you really have to take care of yourself and to take care of your kids," she said. "It really can be life-affirming ... a wonderful second opportunity in your life. It can be actually, I think, very positive."