By using words like honor, I'm trying to avoid using the word eudaimonia again, which is not a particularly common word and yet is most applicable here.
What I mean is, using words like honor, and perhaps words like dignity, truth, virtue, objectivity, etc- there are certain kinds of happiness worth having because it aligns with truth and reality, and there are kinds of happiness that nobody would pick because they are based on false things. Virtually nobody would choose to live a life of happiness that was also based on a lie.
The point of the example is to illustrate that there is more that matters to you than just what you experience. Despite choice a) being the subjectively happier experience, you picked choice b). A person cares not only for the subjective experience of happiness, but also cares that their experience of happiness lines up with reality.
A person who cheats denies their spouse this kind of objective happiness. It renders their happiness the type that isn't based on reality, and isn't the type that most people would choose for their self. If one loves their partner, they would do well to avoid depriving their spouse of the sort of happiness that they would seek.
A person who doesn't wish to define and express their self as someone who is willing to break obligations, promises, and trust whenever they are certain they won't be caught and there won't be tangible consequences, despite the fact that it would hurt the person if they were to know, would do well to avoid cheating. If they care more about objective happiness than simply subjective happiness based on an illusion, and understand that their partner probably feels the same, and if they truly love their partner, why would they cheat?
Thank you Penumbra, the part in bold in particular makes pretty good sense to me.
I'd be making a choice for them that they wouldn't make for themselves, which is unfair.