Unspoken expectations are resentments in waiting. This is the core of the "E" in SEA Change. Most fights aren't about what happened; they're about what was expected and never said.
I (Sean) was a master at this. I'd be fuming that an empty pizza box was on the counter, thinking, "She knows I hate clutter!". But I had never clearly communicated that need. I was mad about a rule I never shared. That is a recipe for resentment.
Application: What is one "rule" you have in your head that you've never actually shared with your spouse?