Epictetus Quote

Let not another's disobedience to Nature become an ill to you; for you were not born to be depressed and unhappy with others, but to be happy with them. And if any is unhappy, remember that he is so for himself; for God made all men to enjoy felicity and peace.

That we ought not to be affected by Things not in our own Power, Chap. xxiv. - Bartlett's Familiar Quotations, 10th ed. (1919)