I snipped this bit from Carolyn's Monday column in the Washington Post. The entire column is good reading IMO.
"Optimism also demands that you greet new people and situations with an open mind, instead of just lumping them into some lazy category of Things You Already Know. When we prejudge, we close doors, deny opportunities, marinate ourselves in the past.
To have an open mind, though, we have to assign ourselves to the role of students in life, and to not knowing the outcome in advance. It's trading the secure (if false) sensation of being wise to everyone and everything, for the possibility of surprise, be it pleasant or un-.
Choosing optimism is choosing vulnerability and humility on an ongoing basis, and that's often in conflict with our nature. "