The Theory of Reasoned Action proposes that behavioral intention is the best predictor of behavior. Behavioral intention is influenced by two factors - attitude, which is one's personal beliefs about performing a behavior, and subjective norms, which is the social pressure one feels about a behavior. Both attitude and subjective norms combine to form behavioral intention, which then predicts whether the behavior will be performed. This theory has been applied to understand and modify behaviors related to health issues like STD/HIV prevention, health/fitness, smoking, and drinking.