From a recent conversation with a friend. Please note, this is not about my relationship or my situation in the slightest.
Fairness with objects: “if you have a cookie, I get a cookie.”
Fairness with human beings: “if you are able to explore new relationships, I am able to explore new relationships.”
Unfairness with objects: “If you ate a cookie and my cookie fell on the floor in the middle of a New York City gutter, you have to find the nearest restroom facility and puke up your cookie.”
Unfairness with human beings: “If my extracurricular relationship fails, you have to end yours.”
tl;dr: People are not objects. Don’t “experiment” with people’s emotions. Learn the difference between fair and idealistic. Recognize when your idealism is actually very unfair (and hurtful) to someone else.