Discourses, "That We Ought Not to be Moved by a Desire of Those Things Which Are Not in Our Power" (§1)

“Let not that which in another is contrary to nature be an evil to you; for you are not formed by nature to be depressed with others nor to be unhappy with others, but to be happy with them. If a man is unhappy, remember that his unhappiness is his own fault; for God has made all men to be happy, to be free from perturbations.”