During my first marriage I strayed - mainly because my wife was not her husband's girlfriend. But that doesn't matter for I was not my wife's boyfriend. And for that I have regrets.
I married the woman with whom I strayed, and got into the stepfamily thing - a challenging situation to say the least. I don't think either of us realized what we were dealing with. On top of that she was my "damsel in distress." And yes, as you predict, she quickly became my distressed damsel. We later divorced, leaving 3 children as victims.
Now the better news...
After the split, I decided to move into an apartment across the street from my kids' school. They could stay over as often as they wanted. Their mom and I had no custody agreement. Nor did we have a child support agreement. Being across from my kids' school allowed me to easily take them to and from their after school activities. I agreed to pay the mortgage of my ex-wife's as long as the children lived there. And I agreed to pay ALL of the children's' expenses - no questions asked. (Finally, I'm doing the RIGHT thing!)
After they got out of school, I re-married. Now I am my wife's boyfriend, and quickly discovered that when I do that, she becomes my girlfriend. And again, I'm doing the right thing.
There are several lessons here - all of which point to the things you harp on (uh.. forget that...I mean "mention") every day on your show. Well it works! Thank you for showing us the "right thing".