Is anyone esle confused about the 'heart attack' scene?

I don't get the thing Harry says to his wife before she has her stress attack. He tells her that John O'Brian (the guy she later has her affair with) said he thinks, "a woman that does a lot for a man can pay a heavy price," when he was drunk. She asks Harry his opinion on what he meant. Harry says he was probably thinking that "if a married man falls in love with another woman, the dedicated wife is surprised and hurt, and she remembers him as he was before they married, and she sees him now as she made him, a better finish product all together, a product another woman is soon going to enjoy." She says he's given this a lot of thought and then starts crying because she thinks he doesn't love her anymore. At first that sounded to me like he was confessing to her he was cheating. I don't understand the meaning of that scene at all. Was it to show Harry trying to let his wife down easy so as to not "shatter her world" as Pierce Brosnan's narration says? Does anyone understand it better?