Max Gunther set forth basic trading principles called The Zurich Axioms:

On Risk:
– Worry is not a sickness but a sign of health – if you are not worried, you are not risking enough.
– Always play for meaningful stakes – if an amount is so small that its loss won’t make any significant difference, then it isn’t likely to bring any significant gains either.
– Resist the allure of diversification.

On Greed: