Optimism bias

 Optimism bias is the demonstrated systematic tendency for people to be overly optimistic about the outcome of planned actions. This includes overestimating the probability of positive events and underestimating that of negative events. Along with the illusion of control and illusory superiority, it is one of the positive illusions to which people are generally susceptible. Excessive optimism can result in cost overruns, benefit shortfalls, and delays when plans are implemented or expensive projects are built. More generally, they are related to the initiation of military conflicts and the creation of economic bubbles.