Meditations, Book 12, Section 2

Marcus Aurelius — The Emperor

There are three things that make up who you are: your body, your life, and your mind. The first two belong to you only in the sense that you must care for them. But the third — your mind — is truly yours. So separate yourself from everything else. Don't dwell on what others do or say. Don't obsess over your past actions and words. Stop worrying about the future. Let go of anything that belongs to your body or your physical life that is beyond your control. Release yourself from whatever happens to you through ordinary human events and accidents. Keep your mind loose and free from all these outside entanglements.

Marcus Aurelius — The Emperor Original

Three things there be in all, which thou doest consist of; thy body, thy life, and thy mind. Of these the two former, are so far forth thine, as that thou art bound to take care for them. But the third alone is that which is properly thine. If then thou shalt separate from thyself, that is from thy mind, whatsoever other men either do or say, or whatsoever thou thyself hast heretofore either done or said; and all troublesome thoughts concerning the future, and whatsoever, (as either belonging to thy body or life:) is without the jurisdiction of thine own will, and whatsoever in the ordinary course of human chances and accidents doth happen unto thee; so that thy mind (keeping herself loose and free from all outward coincidental entanglements;