Tom was a soldier and was often away from home, so it was easy to succumb to temptation. But the second time he had a one-night stand he was filled with remorse.
"The next morning I was off duty and came home. I went to the bedroom and looked down at my wife Mary in the bed, and I remember a voice inside me that said: 'You bastard!'
"I swore then that no matter what opportunity I had, I would never take it again."
He kept the affairs secret for nearly two decades -- then one day something happened that made him tell Mary.
She threw him out of their house. But last week, 10 years later, the day before their 34th anniversary, the couple sat in their Dublin home and told me how they saved their marriage.
Tom and Mary fell in love in their teens, and were married when they were 22. He was part of the Special Forces.
"It had a huge impact," recalls Tom. "I would go out and I could be gone three weeks."
With so much secrecy, it was easy to succumb to other temptations, like the attraction of another woman. Mary sensed something was wrong. Was there another woman? He denied it.
Years passed. Tom left the army. The family grew. Unemployment struck and they had to move to Germany.
The drift in their relationship was widening. Mary was feeling isolated and resentful.
In her mind, she was packing her bags. "It causes a rift, you've mentally left. You're not there giving emotional support."
On their return from Germany, Tom set up his own business, but after some years it failed, catapulting him into a depression. One night Tom had a panic attack that lasted the whole night.
For days, the terrible fear remained. Then he woke up and his mind was clear. He knew he had to tell Mary about his breach of trust 17 years earlier. They went for a walk by the canal, Tom stopped and told her of a one night stand.
"I was gobsmacked," Mary recalls. "I walked away."
Later, Tom told her of another breach in fidelity and she threw him out of the house. For a week he lived with a friend. He wrote apologising to his wife of 24 years and waited.
At home, Mary was taking her own counsel. "It had to be my decision. If you talk to a friend and they're having a bad time, they'll say 'get out'".
She chose to forgive him. They went for counselling but they were still not communicating. And while they shared a bedroom, in Tom's words they were "as far apart as you can get in the same bed".
It took months before he would give her a peck on the cheek: "If I was to kiss Mary, she'd feel I was brushing stuff under the carpet."
When they ultimately began to have a physical relationship, it was scary for them both. "What if it happens again," thought Mary.
One day in church Tom noticed an ad: "Retrouvaille -- a lifeline for troubled marriages."
They were running a weekend shortly after. Immediately he rang Mary and told her about it. The weekend changed their marriage completely.
Three couples who, in Tom's words, "had all been in their own shit," told their own stories, and how they had got back together. Twenty other couples listened to the presentations and worked through the programme.
"I learnt that love is a decision," said Tom.
"We were able to have a proper conversation without blame, that was definitely a start," recalls Mary.
When they started to communicate, both began to learn things about the other.
"I found out things about myself," says Mary. "I was to blame too. We both hurt each other. We could go for weeks without talking."
For Tom it was a revelation. "I never knew my wife. I didn't know the woman who had three children for me."
And now? "I love him more than I did before," says Mary. "I met my soul mate [as a teen] and that's why I wanted to give him another chance."
Her colleagues are surprised at the touches of love -- a poem, or a note that Tom has left in her lunchbox.
Now Tom and Mary help other couples through Retrouvaille. The movement has an astounding 86% success rate. A couple in Cork came back together after a 20-year separation. Honesty, they say, must form the foundation.
"Whether you tell your husband or wife everything is up to you," says Tom, "but you need to start on a better foundation. If you don't remove all the old debris, you are putting new foundations on old debris and the cracks will appear."
"You have to be honest and open. A clean slate, and you can start again."
Retrouvaille weekend for troubled marriages October 14 -- 16, 2011, Dublin. See www.retrouvaille.ie. Tel: 01-4953536.