The antithesis of negativity is not positive thinking, but critical thinking.
Skepticism, rather than optimism, is the most powerful way to undermine pessimistic presuppositions.
The perception of doom and gloom does not arise from a lack of faith in the goodness of the Universe, but from an overabundance of confidence in what we think we already know.
Pessimism, in all of its forms, is a claim to knowledge. And like all claims to knowledge, its premises can be questioned and its assumptions challenged.