In a new interview with Australia's Life magazine, the 68-year-old musician said he covered Waits' song "Picture in a Frame" after the two-week split.
"Penny and I broke up for two weeks and the song is about that time. I asked her for a photo of herself in a frame so that I could see her when I went to bed and when I woke up," he said (via The Mirror).
Stewart, who has had eight children with five women, said he's learned plenty of relationship lessons along the way.
"My relationship rule is, don't argue after a glass of wine -- leave debating until the morning," Stewart said.
"I have always loved women, won some, lost some, but it's not about the magic touch, it's about being a better person and a good listener," he added.