An optimist believes

that we live in the best of all possible worlds;

a pessimist fears that the optimist is correct.

Pessimism and skepticism are

occupational hazards in the repair business

and also

powerful diagnostic tools.

I no longer believe that anything is flat

unless I have rubbed it on my stone.

Eventually the stone will wear out

I suppose

but I've already had this one for years

and use it regularly.