For suppose that every tool we had could perform its task, either at our bidding or itself perceiving the need, and if-like the statues made by Dรฆdalus or the tripods of Hephรฆstus, of which the poet says that "self-moved they enter the assembly of the gods" - shuttles in a loom could fly to and fro and a plectrum play a lyre all self-moved, then master-craftsmen would have no need of servants nor masters of slaves.
AristotleFor 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.
Aristotle