We don’t often think of the 17th century physicist and mathematician as someone who has insight on human relationships.
However, Newton’s third law: every action has an equal and opposite reaction, speaks profound to that realm.
You give a harsh word, and a harsh word is quickly returned.
You give a gracious word, a gracious word is quickly returned.
Although the reaction does not have to be of the same nature as the initial cause, a harsh word can be returned with a gracious one, you can likely testify from experience that it tends to be so.
Newton’s third law is easily seen with physical examples but consider the tremendous impact this has in the context of relationships as well.