The basis for optimism is sheer terror.

May the pain you have known and the conflict you have experienced give you the strength to walk through life facing each new situation with courage and optimism.

A pessimist is an optimist with experience

The basis of optimism is sheer terror.

SIR ROBERT CHILTERN: … But may I ask, at heart, are you an optimist or a pessimist? Those seem to be the only two fashionable religions left to us nowadays.
MRS CHEVELEY: Oh, I'm neither. Optimism begins in a broad grin, and Pessimism ends with blue spectacles. Besides, they are both of them merely poses.
SIR ROBERT CHILTERN: You prefer to be natural?
MRS CHEVELEY: Sometimes. But it is such a very difficult pose to keep up.

(Act I., lines 132-140)

Between the optimist and the pessimist, the difference is droll. The optimist sees the doughnut; the pessimist the hole!