"Cognitve dissonance" is a hypothetical model currently under discussion and test in the behavioral sciences. It is not certain whether the state is genuine and, if it is, that everyone who is a state of denial experiences it before denial or accepting truth.
However, being someone who witnesses a lot of this on a regular basis, I tend to believe that cognitive dissonance is very real. Be that as it may, "cogntive dissonance" means "mental disharmony."
It is the state when a person has two conflicting situations in their minds, both of which they view as fact AND undergo distress, discomfort, pain, or other signs of emotional stress as a result.
The Harry Potter books and films are famous for their CD-inducing formula in which we the audience see each story through the eyes of the protagonist, get fooled into thinking he has made the right conclusions, only to realize he is wrong. At this point Harry has to make a decision how to act, and we the audience are hooked. We have to know the truth and the answers ourselves, so we read on or keep watching, again hooked.
Harry is a hero in that he never stays in his state of cognitive dissonance for very long. He immediately wakes up, ending the cognitive dissonance by decisive action which, because we see each story through his eyes is very satisfying to us.
Note, the actions of Harry Potter after he learns the truth are never done in the state of cognitive dissonance. Harry has found a solution to dealing with two conflicting beliefs, albeit the right one. But the reality is that most people don't immediately respond to cognitive dissonance, and sometimes they stop the stress by denial. Harry is a hero because he does this immediately and always make the right choice in the end.
Three other films baptize their audiences in cognitive dissonance very successfully, namely "Fight Club" and Hitchcock's masterpieces "Vertigo" and "Psycho." Most people describe these films as having "surprise endings," but in reality each ends up telling a completely different or foreign story in the end than the one you believed you started to watch. The cognitive dissonance that results is actually like a thrill ride, and each of these films is highly praised for their conclusion "payoffs." But the conclusions are only satisfying because they relieve the stress they cause.
Cognitive dissonance is only a temporary state, but you are right that it will rise again if you don't stop falling for falsehood that keeps getting proven wrong. But it is still temporary stress, discomfort, a state that seeks immediate relief.