Remember that desire demands the attainment of that of which you are desirous; and aversion demands the avoidance of that to which you are averse; that he who fails of the object of his desires is disappointed; and he who incurs the object of his aversion is wretched. If, then, you shun only those undesirable things which you can control, you will never incur anything which you shun; but if you shun sickness, or death, or poverty, you will run the risk of wretchedness. Remove [the habit of] aversion, then, from all things that are not within our power, and apply it to things undesirable, which are within our power. But for the present altogether restrain desire; for if you desire any of the things not within our own power, you must necessarily be disappointed; and you are not yet secure of those which are within our power, and so are legitimate objects of desire. Where it is practically necessary for you to pursue or avoid anything, do even this with discretion, and gentleness, and moderation.