Meditations 7.16

The ruling faculty does not disturb itself; I mean, does not frighten itself or cause itself pain. But if any one else can frighten or pain it, let him do so. For the faculty itself will not by its own opinion turn itself into such ways. Let the body itself take care, if it can, that it suffer nothing, and let it speak, if it suffers. But the soul itself, that which is subject to fear, to pain, which has completely the power of forming an opinion about these things, will suffer nothing, for it will never deviate into such a judgment. The leading principle in itself wants nothing, unless it makes a want for itself; and therefore it is both free from perturbation and unimpeded, if it does not disturb and impede itself.

Marcus Aurelius, Meditations 7.16, translated by George Long

The ruling Reason is never the disturber of its own peace, never, for instance, hurries itself into lust. But if another can cause it fear or pain, let it do so. For it will not let its own assumptions lead it into such aberrations.

Let the body take thought for itself, if it may, that it suffer no hurt and, if it do so suffer, let it proclaim the fact. But the soul that has the faculty of fear, the faculty of pain, and alone can assume that these exist, can never suffer; for it is not given to making any such admission.

In itself the ruling Reason wants for nothing unless it create its own needs, and in like manner nothing can disturb it, nothing impede it, unless the disturbance or impediment come from itself.

Marcus Aurelius, Meditations 7.16, translated by C. R. Haines