Marcus Aurelius
Meditations 5.9
Be not disgusted, nor discouraged, nor dissatisfied, if thou dost not succeed in doing everything according to right principles, but when thou hast failed, return back again, and be content if the greater part of what thou doest is consistent with man's nature, and love this to which thou returnest; and do not return to philosophy as if she were a master, but act like those who have sore eyes and apply a bit of sponge and egg, or as another applies a plaster, or drenching with water. For thus thou wilt not fail to obey reason, and thou wilt repose in it. And remember that philosophy requires only things which thy nature requires; but thou wouldst have something else which is not according to nature.—It may be objected, Why, what is more agreeable than this [which I am doing]? But is not this the very reason why pleasure deceives us? And consider if magnanimity, freedom, simplicity, equanimity, piety, are not more agreeable. For what is more agreeable than wisdom itself, when thou thinkest of the security and the happy course of all things which depend on the faculty of understanding and knowledge?
Marcus Aurelius, Meditations 5.9, translated by George Long
Do not feel qualms or despondency or discomfiture if thou dost not invariably succeed in acting from right principles; but when thou art foiled, come back again to them, and rejoice if on the whole thy conduct is worthy of a man, and love the course to which thou returnest. Come not back to Philosophy as to a schoolmaster, but as the sore-eyed to their sponges and their white of egg, as this patient to his plaster and that to his fomentations. Thus wilt thou rest satisfied with Reason, yet make no parade of obeying her. And forget not that Philosophy wishes but what thy nature wishes, whereas thy wish was for something else that accords not with Nature. Yes, for it would have been the acme of delight. Ah, is not that the very reason why pleasure trips us up? Nay, see if these be not more delightful still: high-mindedness, independence, simplicity, tenderness of heart, sanctity of life. Why what is more delightful than wisdom herself, when thou thinkest how sure and smooth in all its workings is the faculty of understanding and knowledge?
Marcus Aurelius, Meditations 5.9, translated by C. R. Haines