I am by nature an optimist and by intellectual conviction a pessimist.

I'm not a pessimist at all, but I'm not an optimist, either.

His (my father's) general belief in life's well-being worked either way. 'Have you ever had it before? You have? It's not going to kill you, then. If you've had the same thing before, you'll be alright in the morning.' My mother couldn't have more profoundly disagreed with that. 'You're such an optimist, dear,' she often said with a sigh. 'You're a good deal of a pessimist, sweetheart.' 'I certainly am.' And yet, I was well aware as I stood between them, he the optimist was the one who was prepared for the worst, and she the pessimist was the daredevil.

The optimist says the glass is half full; The security guy says, no glass allowed on the patio!

The optimist says the glass is half full; The pessimist says, no food or drink allowed

The pessimist thinks that, the Apple would sue an apple we eat for having the same name; while optimist thinks that, the Apple would make a 3D printer that would print an apple we eat.