My wife and I are both early 50's and married 21 years before D-Day November 2020 (for those not familiar with infidelity jargon, D-Day stands for "Discovery Day", the day you found out. It's a horrible, horrible day). We have 3 beautiful children.
Probably around year 18 or so, the marriage starts going south, neither of us knows how to fix it, the problems get worse. I make several regrettable mistakes, take her for granted, work too much, focused on my own stuff, don't consider her feelings, control the family money too much. I would later learn in therapy that I was emotionally abusive toward her which was a surprise to me, I would never have considered myself abusive and it certainly didn't feel like it. But things were getting worse.
She was no angel and had hurt me in several ways too, regardless I own all my behavior towards her and knew we needed to fix things. Toward the middle of 2020 I was emotionally shutting down and she had suggested getting help, I knew we needed help but I never took any action. I figured we could get it when I wasn't so busy with work.
Early August 2020 we take a family vacation to a beach condo for 2 weeks. One afternoon at the pool we met Jeff, he was staying in the condo alone for a few months and doing some work in the area. He was nice, the wife and I chatted with him for an hour and then we left and I never saw him again.
End of the vacation we flew home and it was back to typical hectic life.