A nice story taken from http://thedailyenlightenment.com/
On another occasion, Rahula (The only son of Buddha) followed his teacher, Sariputra, on a trip to teach the Dharma. At noon, they begged for alms in the vicinity of Rajagriha. They met a young hooligan, who poured sand on purpose into Sariputra's alms-bowl, and hit Rahula's head with a stick. Blood kept flowing out from the injured part of Rahula's head.
Sariputra comforted Rahula, saying, "Rahula, as disciples of the Buddha, we must cultivate the virtue of patience. We must not be angry with evil people. On the other hand, we should even pity them, because they do not know that every action will produce results, so they commit evil actions."
After listening to Sariputra, Rahula was calm and unruffled. Without uttering a word, he went to the riverbank by himself, and washed away the blood on his head and face. Then, he used his handkerchief to dress the wound. He then continued to beg for alms from others, as if he had not been injured at all.
“Holding on to anger is like grasping a hot coal with the intent of throwing it at someone else; you are the one who gets burned.”
- Lord Buddha
Last year, I experienced extreme anger that I was trembling with rage. For 2 days, my whole mind was obsessed with the anger and how to take revenge against that person. In the end, I decided that it is better to let it go (for the sanity of my mind) and distance myself from that person. Recently, someone shared with me the bad news befell on that person.
Firstly, I do not feel anything (I wasn't happy), as I had already let go of the unhappy incident. Secondly, you always reap what you sow. If his negative behavior is consistent, negative outcome will ripen sooner or later.