"How is it that people remain optimistic even though information challenging those predictions is abundantly available?"

"It turns out it is not commencement speeches or self-help books that make us hopeful. Recently, with the development of non-invasive brain imaging techniques, we have gathered evidence that suggests our brains are hard-wired to be unrealistically optimistic. When we learn what the future may hold, our neurons efficiently encode unexpectedly good information, but fail to incorporate information that is unexpectedly bad."

(NYT link.)