The man who is a pessimist before 48 knows too much; if he is an optimist after it he knows too little.

The man who is a pessimist before forty-eight knows too much; if he is an optimist after it he knows too little

It's better to be an optimist who is sometimes wrong than a pessimist who is always right

Optimist: Day-dreamer more elegantly spelled

There is no sadder sight than a young pessimist, except an old optimist

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