As a study by UCLA found in 2007, the human brain is wired to over-estimate the size of risks, underestimate your abilitytohandle them and downplay the costs of not taking them.
Using the latest brain imaging technologies, researchers have been able to prove that we human beings are neurologically wired to over-estimate the size of risks, under-estimate our abilitytohandle them, and downplay the costs of inaction.