You need to use anger in the right way in the right quantities.

Once a sadhu – a wandering mendicant, was passing through a village, when he received a complaint from the villagers about a cobra that was playing havoc with their lives.
The sadhu was known to have the power to communicate with animals, so they begged him to convince the cobra to spare the villagers.
So the sadhu spoke to the cobra, and the cobra promised not to bite any of the villagers anymore.
A few months later, the sadhu was passing through the same village when he came upon the cobra, badly bruised and almost dead.
“What happened to you? Why are you hurt?” Asked the sadhu.
The cobra cried, “O sadhu! It is you who made me promise never to bite the villagers! I have kept my promise to this day. But the villagers, who were earlier in fear of me, took my mildness to be my weakness. Seeing that I don’t bite, they started torturing me everyday. See what a state I have been reduced to!”
The sadhu replied, “My poor foolish friend! I only asked you not to bite the people. Did I ask you not to hiss at them?”