Adversity is the only balance to weigh friends. - Plutarch

three things must meet together, natural ability, theory, and practice. By theory I mean training, and by practice working at one's craft.

So long as he was personally present, [Alcibiades] had the perfect mastery of his political adversaries; calumny only succeeded in his absence.

When someone blamed Hecataeus the sophist because that, being invited to the public table, he had not spoken one word all supper-time, Archidamidas answered in his vindication 'He who knows how to speak, knows also when'.