There are things which are within our power, and there are things which are beyond our power. Within our power are opinion, aim, desire, aversion, and, in one word, whatever affairs are our own. Beyond our power are body, property, reputation, office, and, in one word, whatever are not properly our own affairs.
Aiming, therefore, at such great things, remember that you must not allow yourself any inclination, however slight, toward the attainment of the others; but that you must entirely quit some of them, and for the present postpone the rest.
Seek at once, therefore, to be able to say to every unpleasing semblance, "You are but a semblance and by no means the real thing." And then examine it by those rules which you have; and first and chiefly by this: whether it concerns the things which are within our own power or those which are not; and if it concerns anything beyond our power, be prepared to say that it is nothing to you.