Law 39
Anger and emotion are strategically counterproductive. You must always stay calm and objective. But if you can make your enemies angry while staying calm yourself, you gain a decided advantage. Put your enemies off-balance. Find the chink in their vanity through which you can rattle them and you hold the strings. –Robert Greene, The 48 Laws of Power (review)
Proverbs 14:29
He who is slow to anger has great understanding,
But he who is quick-tempered exalts folly.
Proverbs 16:32
He who is slow to anger is better than the mighty,
And he who rules his spirit, than he who captures a city.