And thou wilt give thyself relief if thou doest every act of thy life as if it were the last, laying aside all carelessness and passionate aversion from the commands of reason, and all hypocrisy, and self-love, and discontent with the portion which has been given to thee.

Marcus Aurelius (AD 121-180) Roman emperor (161-180), Stoic philosopher

Meditations, Book 2, #5 [tr. Long (1862)]
    (Source)

Usually modernized, "And you will give yourself relief, if you do every act of your life as if it were the last, laying aside all carelessness and passionate aversion from the commands of reason, and all hypocrisy, and self-love, and discontent with the portion which has been given to you," and the source of the more common (and mixed-message) reduction of this aphorism, "Do every act of your life as if it were your last."

Alternate translations:

Go about every action as thy last action, free from all vanity, all passionate and wilful aberration from reason, and from all hypocrisy, and self-love, and dislike of those things, which by the fates or appointment of God have happened unto thee.
[tr. Casaubon (1634), #2]

Perform every action as if it were your last; if your appetites and passions do not cross upon your reason; if you keep clear of rashness, and have nothing of insincerity and self-love to infect you, and do not complain of your destiny.
[tr. Zimmern (1887)]

Do each act as though it were your last, freed from every random aim, from wilful turning away from the directing Reason, from pretence, self-love and displeasure with what is allotted to you.
[tr. Farquharson (1944)]

Approach each action as though it were your last, dismissing the wayward thought, the emotional recoil from the commands of reason, the desire to create an impression, the admiration of self, the discontent with your lot.
[tr. Staniforth (1964)]

Perform every action in your life as if it were your last, putting aside all aimlessness and emotional resistance to the choices of reason, and all pretense, selfishness, and discontent with what has been allotted to you.
[tr. Needleman/Piazza (2008)]