This isnt what I think but I am considering the question in am abstract way based on another thread I read.
So imagine you have a relationship and both parties want to be in the relationship because they love each other.
Imagine person A massively lets themself go or becomes too lazy/not really in the mood to have sex most of the time. This leaves person B with the option of either cheating or walking away from an otherwise good relationship.
Im not talking about temporary dips or periods that can be explained by illness, depression, bereavement but basically just when person A can't be fucked anymore with keeping themself looking their best and putting a bit of energy into their sex life.
Considering a relationship is basically like an unspoken contract, cheating is breaking that contract, but isn't removing all attractive/sexual aspects of the relationship just another way of breaking that contract too?
I guess in a way I'm asking if cheating is ever truly justified.