Yay world!

Being an optimist is logically better than being a pessimist.

Consider: If the pessimists are right

Modern appearances of human improvement are largely illusory, and the world will spiral into self-destruction one way or another. When that happens we find out the pessimists were right, but in the meantime the optimists lead happier lives with the illusion. At best, the pessimists get a moment of victory when they get to say "I told you so" but it doesn't save them from humanity's fate.

Consider: If the optimists are right

The optimists lead contented and fulfilling lives in helping make the world a better place. The pessimists lead lives of the ultimate futility. Skeptical and cynical of an existence when there was never even any need to be they spend their lives thinking "it's all going to turn to shit soon", and it never does.

So, little is to be gained by being a pessimist even if you turn out to be right, and much is lost if you're wrong. Whereas, something is gained by being an optimist either way.

Better to be an optimist, QED.