"Lying to yourself to feel better"
In Aesop's fable, a fox can't reach grapes and decides they must be sour anyway. Leon Festinger called this Cognitive Dissonance. It is the mental stress we feel when we hold two contradictory beliefs or when our actions contradict our values (e.g., "I love animals" vs. "I eat meat").
To reduce this stress, we usually don't change our behavior (which is hard); we change our beliefs (which is easy). Smokers convince themselves "it won't happen to me." Cult members whose doomsday prediction fails believe "our prayers saved the world." We are not rational animals; we are rationalizing animals.