I have not contributed to this thread thus far, having enjoyed what everyone else has supplied. So I guess it's about time to put in my favorite set of maxims, which is not a one-liner.

To ride abroad redressing human wrongs,
To speak no slander, no, nor listen to it,
To honor his own word as if his God's,
To lead sweet lives in purest chastity,
To love one maiden only, cleave to her,
And worship her by years of noble deeds,
Until they won her; for indeed I knew
Of no more subtle master under heaven
Than is the maiden passion for a maid,
Not only to keep down the base in man,
But teach high thought, and amiable words
And courtliness, and the desire of fame,
And love of truth, and all that makes a man.

-- Tennyson, Idylls of the King