It could be part of the character of Minnesotans. I remember in 1987, when the Twins reached the postseason the attitude was "well isn't that nice, I just hope the boys don't embarrass themselves," then "hey, they actually won a game, won't be a sweep," then "whoa, two wins, what is this?", then "I see the Tigers won a game, looks like the luck has run out," et cetera, right up through the World Series win. You want real pessimism, try Philly or Boston.