Om Swami
How can I stay calm instead of reacting with anger to someone's behaviour?
Equanimity: everyone bears their own karma
There is a third path, samata, or equanimity: each person is the heir of their own actions and pays for them, and so do you. Getting angry means losing before the battle is fought.
That is, the third path is the path of equanimity: I must stay even, because this person is the heir of their own actions.