Minimalization is the human tendency to believe that a situation is not as serious as it seems. As a simplistic example, a person might come to find a leaking water heater in their closet. At first they might say (and even believe) that it's a one time issue that won't occur again and it's just a matter of letting the carpet dry out. Eventually, after this happens a few times, they find damaged wood in the floor and mold growing, fully realizing their water heater is broken. This initial behavior of not thinking a problem existed was an example of minimalization. Minimalization probably evolved as a defense mechanism to save the person from excessive stress and worry.