Great expectations... but little to come?

Throughout the entire day, both students and teachers were buzzing around on excitement [espresso :)]. Not only are the holidays and winter break just around the corner, but there has been an underlying anticipation for, you guessed it, the snow day. Don't deny it-- you know you've considered how awesome it would be to start break a day early: no last-minute tests, no homework, and absolutely no teachers. Just you and your pillow together at last. However, reasoning comes over you and tells you that there most likely won't be a snow day and that you shouldn't get your hopes up.

But that's exactly it: you shouldn't get your hopes up. Why? Because you know that if it turns out that we don't have a snow day you'll be royally ticked off. And if you keep your hopes low, let's just say you won't be a happy camper. Is it just human nature to create images like this to alleviate distress? Why do we constantly set up false ideas when we know that they will make us feel worse than we did in the first place? 

Now let's flip perspectives. Is it considered pessimism when you purposefully keep your expectations low so that there will be no hard feelings? Based on my own experiences I have learned to keep my expectations low to prevent myself from totally losing it (which I can't say that I haven't done already). What is your opinion? Do you keep your expectations high or low?Do you think it determines whether a person is optimistic or pessimistic?