Man must consider, not only that each day part of his life is
spent, and that less and less remains to him, but also that, even if
he live longer, it is very uncertain whether his intelligence will
suffice as heretofore for the understanding of his affairs, and for
grasping that knowledge which aims at comprehending things human and
divine. When dotage begins, breath, nourishment, fancy, impulse, and
so forth will not fail him. But self-command, accurate appreciation of
duty, power to scrutinize what strikes his senses, or even to decide
whether he should take his departure, all powers, indeed, which demand
a well-trained understanding, must be extinguished in him. Let him be
up and doing then, not only because death comes nearer every day, but
because understanding and intelligence often leave us before we die.
Marcus Aurelius, Meditations (III,1)
Marcus Aurelius, Meditations (III,1)