From Voltaire, Candide, http://www.literature.org/authors/voltaire/candide/chapter-30.html
In the neighborhood lived a famous dervish who passed for the best philosopher in Turkey; they went to consult him: Pangloss, who was their spokesman, addressed him thus:
"Master, we come to entreat you to tell us why so strange an animal as man has been formed?"
"Why do you trouble your head about it?" said the dervish; "is it any business of yours?"
"But, Reverend Father," said Candide, "there is a horrible deal of evil on the earth."
"What signifies it," said the dervish, "whether there is evil or good? When His Highness sends a ship to Egypt does he trouble his head whether the rats in the vessel are at their ease or not?"
"What must then be done?" said Pangloss.
"Be silent," answered the dervish.
(I believe in the original the dervish says "te taire," which could be translated as "shut up!")
Then they go on to meet a gardener, who says he doesn't mind what happens in the kingdom but cultivates his garden the best he can. And maybe that is the best I can do. I am not in charge of what I am not in charge, and usually I do not know what's best.