When I get into a particular negative emotional state, I make up reasons that I feel that way. When I start a sentence with a bitter "Fine!" or "I should have known better," it's a guarantee that the next statement out of my mouth ("you obviously don't care", "there's no point in cooking for you because you hate food," etc.) will be something I know to be false but that, if it were true, would explain why I feel rotten. Physically, the cue is me turning away from the person I'm speaking to. The actual explanation, "I like tomatoes, and I want you to like them too" or "I'm tired" or "My brain chemistry might be out of whack" are not as satisfying to say out loud as a condemnation of the other person.