I don't believe love just goes away. And fretting over why people just stop loving someone usually boils down to people not knowing what true love is, so they don't know how to give it. Nor do they understand, it's a verb, a conscious CHOICE, and it's the only choice on the face of this planet that means anything at all. It's the foundation of your legacy and the gauge of the worth of the dash on your headstone. My dash will be epic.
It is the responsibility of the cheater not the other person except, that other person is liable as he/she knew that there was a family behind the relationship that they could care less about. Thus the saying homewrecker