There is a concept in game theory that, simplistically put, states that if two people are playing the best strategy they can, with no rational way to change, they will stay in equilibrium even if an overall change could be beneficial to both players.

The mother of my heart passed away this week.

I suppose I could use terms like "mother-in-law." I could further compound it by using the proper term "stepmother-in-law." Or I could confuse it by telling you what I always called her -- Mom.