"If ever a man and his wife, or a man and his mistress, who pass nights as well as days together, absolutely lay aside all good breeding, their intimacy will soon degenerate into a coarse familiarity, infallibly productive of contempt or disgust"

This quote by Lord Chesterfield is an alerting about the effects of overlooking good manners in a relationship. He suggests that if a couple, whether wed or not, stops working to maintain great manners and politeness in their interactions, their relationship will rapidly end up being stretched and unpleasant. This is due to the fact that familiarity can result in a lack of respect and appreciation for one another, which can cause contempt and disgust. Lord Chesterfield is emphasizing the significance of good manners and politeness in relationships, as it is necessary for keeping a healthy and considerate connection. Without good manners, relationships can rapidly become strained and undesirable.