A person came to the Prophet and said: Copy Arabic text "O Prophet, give me an advice. Let it be short so that I do not forget it. The advice should be such that I am able live by it." 
The Prophet replied: "Do not be angry." (Muwatta Imam Malik 1891)

In social life when you live alongside people, you may constantly face situations that make you angry. You may be hurt by what someone says. On these occasions, you must swallow your anger. You must never get offended. You should not get offended, you must not become negative. Your mind shouldn’t be disturbed. You must maintain your positivity. Your positive thinking must continue on a non-stop basis. What is this?
This is great wisdom. The human mind is constantly thinking. When you sleep at night, your mind continues to think. This happens throughout your lifetime, either consciously or unconsciously. What disturbs this thinking process is anger. Anger means when you get offended, your mind gets disturbed. The moment of anger disturbs your thinking process.  
Your intellectual process is the source of wisdom. The thinking process going on in your mind unfolds the hidden treasures. This process extracts wisdom from the world. Just as the honeybee extracts nectar from the flower, the mind extracts wisdom from the world.  All these things keep going on in the human mind. But when you get disturbed, negative or offended, your thinking process stops. It will be a huge loss for a person to have his thinking process stopped.