Here are some of my favorites-some original, some not:

If you think something is wrong-it probably is.

Guilt is a many-splendored thing.

There are worse things than being alone...like wishing you were.

Blessed is he who expects nothing, for he shall never be disappointed. (Benjamin Franklin)

Three people can keep a secret...if two of them are dead (Benjamin Franklin)

People are about as happy as they make up their minds to be. (Abraham Lincoln)