Cicero (106 B.C. — 43 B.C.) was a man that had great influence in his time in the roman empire. That is, until he was killed for being a political pain-in-the-ass. (Though Marc Antony got pretty much served by Cicero's son for having him killed )
However, the man did something truly epic: He read, studied and found 6 common flaws which mankind exhibited over all of known history. A testament to their correctness is that they still apply today.
The Six Mistakes of Man
1. The illusion that personal gain is made up of crushing others.
2. The tendency to worry about things that cannot be changed or corrected.
3. Insisting that a thing is impossible because we cannot accomplish it.
4. Refusing to set aside trivial preferences.
5. Neglecting development and refinement of the mind, and not acquiring the habit of reading and study.
6. Attempting to compel others to believe and live as we do.
Amazing, isn't it? This is the stuff I would love to have learned earlier in life.