Some more on cognitive dissonance from Wikipedia.

"Cognitive dissonance is a state of opposition between cognitions. For the purpose of cognitive consistency theory, cognitions are defined as being an attitude, emotion, belief or value, although more recent theories, such as ecological cognition suggest that they can also be a goal, plan, or an interest. In brief, the theory of cognitive dissonance holds that contradicting cognitions serve as a driving force that compels the human mind to acquire or invent new thoughts or beliefs, or to modify existing beliefs, so as to minimize the amount of dissonance (conflict) between cognitions...The more well-known form of dissonance, however, is post-decisional dissonance. Many studies have shown that people with compulsive disorders like gambling will subjectively reinforce decisions or commitments they have already made. In one simple experiment, experimenters found that bettors at a horse track believed bets were more likely to succeed immediately after being placed. According to the hypothesis, the possibility of being wrong is dissonance-arousing, so people will change their perceptions to make their decisions seem better."