Meditations 5.26

Let the part of thy soul which leads and governs be undisturbed by the movements in the flesh, whether of pleasure or of pain; and let it not unite with them, but let it circumscribe itself and limit those affects to their parts. But when these affects rise up to the mind by virtue of that other sympathy that naturally exists in a body which is all one, then thou must not strive to resist the sensation, for it is natural: but let not the ruling part of itself add to the sensation the opinion that it is either good or bad.

Marcus Aurelius, Meditations 5.26, translated by George Long

Let the ruling and master Reason of thy soul be proof against any motions in the flesh smooth or rough. Let it not mingle itself with them, but isolate and restrict those tendencies to their true spheres. But when in virtue of that other sympathetic connection these tendencies grow up into the mind as is to be expected in a single organism, then must thou not go about to resist the sensation, natural as it is, but see that thy ruling Reason adds no opinion of its own as to whether such is good or bad.

Marcus Aurelius, Meditations 5.26, translated by C. R. Haines