"Do not get angry." لا تغضب
According to many scholars, this Hadith has two meanings:
1. Don't put yourself in a situation that makes you angry.
2. Don't lose your control if you do get angry.
Anger is a natural human emotion and we all feel it sometimes. For example, the Qur'an talks about prophet Musa being angry at his people when they worshiped an idol in his absence. The important thing then is to learn how to deal with anger and not let it get the upper hand. To this effect, the prophet recommended doing the following at times of anger:
1. Remember Allah and seek refuge in him from shaytan.
2. Change position and/or environment.
3. Perform wudu (ablution) or take a shower or bath.
4. Be silent.
Anger is not always negative. In fact it's important to get angry sometimes. It's been reported that the prophet would never take revenge for himself but he would get angry and revenge when Allah's right is violated. He's also reported to have expressed anger for his daughter.