There must be logical minds among all species if they hope to survive. Not everyone can be bridled with hope and optimism.

He who has never hoped can never despair

The optimist's hope and the pessimist's despair: reciprocal illusions.

Keep a light, hopeful heart. But ­expect the worst.

Optimism is denial for chumps with no life experience".
"What's pessimism?" I said.
"Religion without God.

So desperate was Kugel for things to turn out for the best, proclaimed Professor Jove, that he couldn't stop worrying about the worst. Hope, said Professor Jove, was Solomon Kugel's greatest failing.