Most people overrate their own abilities and exaggerate their capacity to shape the future. That’s fine. Optimistic people rise in this world. The problem comes when these optimists don’t look at themselves objectively from the outside.

The planning fallacy is failing to think realistically about where you fit in the distribution of people like you. As Kahneman puts it, “People who have information about an individual case rarely feel the need to know the statistics of the class to which the case belongs.”

via The Planning Fallacy – NYTimes.com.