If happiness is activity in accordance with excellence, it is reasonable that it should be in accordance with the highest excellence.

For both excessive and insufficient exercise destroy one's strength, and both eating and drinking too much or too little destroy health, whereas the right quantity produces, increases and preserves it. So it is the same with temperance, courage and the other virtues. This much then, is clear: in all our conduct it is the mean that is to be commended.

To write well, express yourself like the common people, but think like a wise man.

Speech is the representation of the mind, and writing is the representation of speech.

In order to be effective you need not only virtue but also mental strength.

...The entire preoccupation of the physicist is with things that contain within themselves a principle of movement and rest.

To be always seeking after the useful does not become free and exalted souls.