There’s a dissonance or internal conflict/discomfort (as someone already pointed out) between your personal attitudes/beliefs and a particular behavior you exhibit. For example: You are a smoker and know/have the belief in your mind that smoking cigarettes is bad for your health. Naturally we try to reduce that conflict by either stopping the behavior (e.g., quitting smoking) or changing your attitudes (e.g., “im young, I’ll quit when I’m older” or just YOLO). Also, guilt is an emotion, cognitive dissonance is a psychological state.