Psychologically speaking, is Christianity based more on optimism or pessimism?

I've been called pessimistic for not believing in Christianity, but does the faith really personify any veritable form of optimism? It seems that it almost requires a belief that the earth and basically everyone on it have to be corrupt in order for it to make sense that they should be saved, and that the earth itself should be forsaken for some other place in the clouds. Scholars have even called it a 'preaching of death', or at least as an alternative take on reality, as a means to 'purity' or nothingness, which tends to allude to pessimism.