Meditations 8.41

Hindrance to the perceptions of sense is an evil to the animal nature. Hindrance to the movements [desires] is equally an evil to the animal nature. And something else also is equally an impediment and an evil to the constitution of plants. So then that which is a hindrance to the intelligence is an evil to the intelligent nature. Apply all these things then to thyself. Does pain or sensuous pleasure affect thee? The senses will look to that. Has any obstacle opposed thee in thy efforts towards an object? If indeed thou wast making this effort absolutely [unconditionally, or without any reservation], certainly this obstacle is an evil to thee considered as a rational animal. But if thou takest [into consideration] the usual course of things, thou hast not yet been injured nor even impeded. The things however which are proper to the understanding no other man is used to impede, for neither fire, nor iron, nor tyrant, nor abuse, touches it in any way. When it has been made a sphere, it continues a sphere.

Marcus Aurelius, Meditations 8.41, translated by George Long

To the animal nature a thwarting of sense-perception is an evil, as is also to the same nature the thwarting of impulse. There is similarly some other thing that can thwart the constitution of plants and is an evil to them. Thus then the thwarting of intelligence is an evil to the intelligent nature. Transfer the application of all this to thyself. Does pain, does pleasure take hold of thee? The senses shall look to it. Wast thou impelled to a thing and wast thwarted? If thy impulse counts on an unconditional fulfilment, failure at once becomes an evil to thee as a rational creature. But accept the universal limitation, and thou hast so far received no hurt nor even been thwarted. Indeed no one else is in a way to thwart the inner purposes of the mind. For it no fire can touch, nor steel, nor tyrant, nor obloquy, nor any thing soever: a sphere once formed continues round and true.

Marcus Aurelius, Meditations 8.41, translated by C. R. Haines