Cognitive Dissonance

When our beliefs and our behavior conflict, we feel psychological discomfort — and we relieve it by changing our beliefs to fit our behavior, rather than changing the behavior.

• A smoker who knows smoking is deadly convinces himself it's not that dangerous, or that he'll quit soon, or that he has good genes.
• A person who joins an expensive cult and finds it disappointing upgrades their opinion of the group — to justify the cost of joining.
• An investor who makes a clearly bad trade reframes it as a 'long-term strategic position' to avoid the psychological pain of admitting the mistake.