Or so she thought.
Upon returning from their holiday, Anderson writes that she and her husband took a walk through a lavender field near their home. Bathed in a "perfect" light, she decided to take a series of selfies of the two of them.
Later, when she downloaded the images to her computer, she was "jolted" by one in particular.
"In the picture, the sun was blazing and Peter was looking directly at me with an expression unlike any I'd seen before.
"It can only be described as thinly-veiled contempt - there was a sneer on his lips and a strange look in his eyes, as though he hated me. I was smiling at the camera in my sundress, unaware. In that moment, I knew our marriage was over," she wrote.
Anderson reveals that five years earlier, her husband had had an affair with a colleague. She forgave him and they moved on. But suddenly she was reminded of his moodiness, similar to his behaviour before their holiday, and wondered if he was cheating again.
Later that night, when he was in the bathroom, Anderson trawled his work phone. "There I found a text message, sent the previous week, arranging to meet the same colleague he'd had the affair with all those years ago."
When she confronted him, he became defensive and told her he had heard the woman had cancer and wanted to find out how she was.
"The fact he could lie so swiftly and easily stung almost as much as the infidelity," she writes.
After describing an initial feeling of numbness, she calmed down and two days later asked him to move out.
Anderson writes that she was "furious" that it had taken "a photo to shake me out of my naivety."
But there was another issue that gave rise to greater anger in her. She had given up children for Peter, nine years her senior.
When they met, he already had an adult daughter and didn't want more children. Anderson reluctantly agreed, consoled by the idea that the two of them "would be enough."
In the days after Peter left, Anderson reveals she "couldn't get out of bed, barely ate or slept, and my hair began falling out." She also started seeing a counsellor.
A few months on, she came to realise how miserable she had really been with her husband and how much her self-esteem had been "eroded".
She explains how she started going out by herself, to the theatre, on holidays, and began to consider her future on her own.
Anderson, 50, has come to terms with the fact that she can't have children. And while she'd "like to find a partner" she's in no hurry. She's making the most of her own time.
And that photo has been "deleted forever".
*Erin Anderson's name has been changed
