Discourses, "That We Ought Not to be Moved by a Desire of Those Things Which Are Not in Our Power" (§4)

“So in this matter also: if you kiss your own child, or your brother or friend, never give full license to the appearance, and allow not your pleasure to go as far as it chooses; but check it, and curb it as those who stand behind men in their triumphs and remind them that they are mortal. Do you also remind yourself in like manner, that he whom you love is mortal, and that what you love is nothing of your own; it has been given to you for the present, not that it should not be taken from you, nor has it been given to you for all time, but as a fig is given to you or a bunch of grapes at the appointed season of the year.”