It’s tough to repair a marriage following infidelity, even if both parties really want to. I’ve seen it over and over, variations on a theme:
Frankie cheats, and then says Sorry, and means it. But doesn’t address the root causes of the cheating, so Sorry doesn’t do much good. Johnnie wants to trust again, but knows better.
Or Frankie not only says Sorry but also goes to therapy and insists that progress is being made so that cheating will not be such a pressing temptation in the future. Johnnie wants to trust again, and appreciates the effort, but doesn’t actually see any progress.