Socrates (469 BC - 399 BC)

By all means marry; if you get a good wife, you'll be happy. If you get a bad one, you'll become a philosopher.

Death may be the greatest of all human blessings.

Do not do to others what angers you if done to you by others.

Envy is the ulcer of the soul.

Get not your friends by bare compliments, but by giving them sensible tokens of your love.

Regard your good name as the richest jewel you can possibly be possessed of - for credit is like fire; when once you have kindled it you may easily preserve it, but if you once extinguish it, you will find it an arduous task to rekindle it again. The way to gain a good reputation is to endeavor to be what you desire to appear.

Remember that there is nothing stable in human affairs; therefore avoid undue elation in prosperity, or undue depression in adversity.

Remember what is unbecoming to do is also unbecoming to speak of.

The only good is knowledge and the only evil is ignorance.
 
The shortest and surest way to live with honor in the world, is to be in reality what we would appear to be; and if we observe, we shall find, that all human virtues increase and strengthen themselves by the practice of them.

Think not those faithful who praise all thy words and actions; but those who kindly reprove thy faults.

Thou soundest eat to live; not live to eat.

Having the fewest wants, I am nearest to the gods.

I know nothing except the fact of my ignorance.

There is only one good, knowledge, and one evil, ignorance.

Bad men live that they may eat and drink, whereas good men eat and drink that they may live.

I am not an Athenian or a Greek, but a citizen of the world.

I decided that it was not wisdom that enabled [poets] to write their poetry, but a kind of instinct or inspiration, such as you find in seers and prophets who deliver all their sublime messages without knowing in the least what they mean.
 
The hour of departure has arrived, and we go our ways - I to die, and you to live. Which is better God only knows.

The unexamined life is not worth living for man.

I do nothing but go about persuading you all, old and young alike, not to take thought for your persons or your properties, but and chiefly to care about the greatest improvement of the soul. I tell you that virtue is not given by money, but that from virtue comes money and every other good of man, public as well as private. This is my teaching, and if this is the doctrine which corrupts the youth, I am a mischievous person.

The hour of departure has arrived, and we go our ways--I to die and you to live. Which is the better, only God knows.