As children, we are told that we must be "fair" to other people, and that usually involves treating them the way we would want to be treated. So, when we start dating, most of us believe that relationships should be "fair." For most, that implies that both participants should make a substantially equal effort for their partner. But some people have different ideas about what "fairness" means, and some people get extremely upset when they decide their partner isn't being "fair."
All relationships can't always be fair. I am getting married on April 27 and my fiancee (who lived in China until she was 29 years old) knows NOTHING about American weddings, and that is what she wants: an American wedding. So I must do all of the planning. I could complain that isn't fair, but what does that accomplish?
I think "fair" isn't a useful concept for relationships. It should be replaced with two questions: are you getting your needs met in the relationship, and is your partner usually contributing to the best of his or her abilities? If the answers are "yes" and "no," then it is most likely a healthy relationship. What do you think?