The gorilla in the middle of many relationship rooms is monogamy (or lack of). People’s attitudes on monogamy differ based on their definitions of intimacy and their buy-in to the relationship’s contract. In a harmonious relationship the partners agree on definitions of intimacy and contracts. People really vary here. There are swingers (who’s on the menu tonight?) who are happy with other swingers and puritans (sex only for procreation!) who are happy with puritans. The disharmony shows up when you mix the swingers with the puritans.
The concept of Love has a strange connection to the intimacy definitions and sexual contracts. A person can very much love another, but not enter a relationship because they know their definitions and contracts are different. Outside of dogmatic moralities and hygienic common-sense, there is no right and wrong to where people draw their own lines of intimacy. The right and wrong enters when we relate to others intimately. The moralities, emotional needs, and hygienic manners define the expectations of the relationship, and from that, the behavior of the two people involved.
The two separate people become one, even as they are still striving to honor themselves. This can be done harmoniously or disharmoniously. Harmonious is good. Disharmonious can be destructive to all involved. There is a place to walk away from a relationship, or never enter it at all, if the incompatibles between the two people do not promote mutual growth. It can be from a place of Love that a person walks away from another. The honoring of oneself, and the relationship as a whole, can dissolve the same relationship. This does not happen in an environment of comfort or satisfaction. It instead occurs in that space of hard change and observation of the paradoxes of the Divine.