Is Happiness a Mental Disorder?
“We have a tendency to regard people in their ordinary moods as rational information processors, relatively free of systematic bias and distorted judgments… much research suggests that when they are not depressed, people are highly vulnerable to illusions, including unrealistic optimism, overestimation of themselves, and an exaggerated sense of their capacity to control events. The same research indicates that depressed people’s perceptions and judgments are often less biased.” Lauren Alloy
This idea actually has a name: depressive realism.