Good day turned bad

Why do relationships have a certain element of suffering? When they are in a bad mood, somehow your mood shifts as well, whether you wanted it to or not? You planned on having a good day, despite grinding your teeth the entire night before because of all the huffing and puffing beside you. You were goingto have a good, or so you thought. I wanted to be in a good mood today, but now I'm not I cant stand it!