I'd rather think about it as lowering expectations. If you predict gloom, and then things turn up not as gloomy, there will be a reason to have a brighter look on life.
I am by nature a believer in the ultimate goodness in human nature (if it is given a chance) and an optimist - I usually believe that justice will eventually prevail, albeit it may take a while. What baffles me is a wide spread resistance to thinking outside the box and conventional beliefs, the inability to see the big picture, or rather mistaking a small picture for the big one and the irrational fear of the unfamiliar - which IMHO creates fertile ground for demagogues and fascists to thrive - but that is another story.
People need a constant reminder that they are not the center of the universe, that there are things bigger than themselves, and that there are things of which they have not even dreamed of. That function was typically performed by religion and culture - but in this society both have become commodities custom-tailored to individual preferences, and thus lost their navel-gazing-shattering capabilities. Hence my conclusion that only disasters can perform that function - to make people stop, look around with awe and realize that their bellies are not the center of the universe.
Wojtek