"Speeches of Isocrates"

“Consider that nothing in human life is stable; for then you will not exult overmuch in prosperity, nor grieve overmuch in adversity. Rejoice over the good things which come to you, but grieve in moderation over the evils which befall you, and in either case do not expose your heart to others; for it were strange to hide away one's treasure in the house, and yet walk about laying bare one's feelings to the world.”

“Always when you are about to say anything, first weigh it in your mind; for with many the tongue outruns the thought. Let there be but two occasions for speech — when the subject is one which you thoroughly know and when it one on which you are compelled to speak. On these occasions alone is speech better than silence; on all others, it is better to be silent than to speak.”

“Never hope to conceal any shameful thing which you have done; for even if you do conceal it from others, your own heart will know. … Pursue the enjoyments which are of good repute; for pleasure attended by honor is the best thing in the world, but pleasure without honor is the worst.”

“Plutarch", Life of Isocrates”

“Guard yourself against accusations, even if they are false; for the multitude are ignorant of the truth and look only to reputation. In all things resolve to act as though the whole world would see what you do; for even if you conceal your deeds for the moment, later you will be found out. But most of all will you have the respect of men, if you are seen to avoid doing things which you would blame others for doing.”

“… all men will be grateful to you: the Hellenes for your kindness to them and the rest of the nations, if by your hands they are delivered from barbaric despotism and are brought under the protection of Hellas.”