Cognitive dissonance is a term in psychology that describes an uncomfortable feeling of having two conflicting thoughts simultaneously. One can solve the "tension" this creates by changing one of the thoughts. E.g. "It is dangerous to smoke" and "I smoke". Since these ideas may create discomfort, you can either quit smoking, which is difficult, or you may think that smoking is not that dangerous. Actually, those who smoke does not think smoking is as dangerous as those who do not smoke. One possible explanation is cognitive dissonance! This video is a bit old, but in it Jon Stewart explains the concept in his own way:)