To live happily is an inward power of the soul, when she is affected with indifferency, towards those things that are by their nature indifferent.
 Marcus Aurelius, Meditations (c. 170 - 180). copy citation

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Author Marcus Aurelius
Source Meditations
Topic power soul
Date c. 170 - 180
Language English
Reference
Note Translated by Meric Casaubon
Weblink https://en.wikisource.org/wiki/Marcus_Aurelius_Antoninus_-_His_Meditatio...

Context

“Above all things, that must be avoided. However true goodness, simplicity, and kindness cannot so be hidden, but that as we have already said in the very eyes and countenance they will show themselves. XV. To live happily is an inward power of the soul, when she is affected with indifferency, towards those things that are by their nature indifferent. To be thus affected she must consider all worldly objects both divided and whole: remembering withal that no object can of itself beget any opinion in us, neither can come to us, but stands without still and quiet;” source