Anguttara Nikaya:
"There are three types of people in the world. What three?
One who is like carving on a rock, one who is like scratching on the ground, and one who is like writing on the water.
What sort of person is like carving on a rock?
Imagine a certain person who is always getting angry and his anger lasts long, just as carving on a rock is not soon worn off by wind, water or lapse of time.
What sort of person is like scratching on the ground?
Imagine a certain person who is always getting angry but his anger does not last long, just as scratching on the ground is soon worn off by the wind, water and lapse of time.
And what sort of person is like writing on the water?
Imagine a certain person who, even though spoken to harshly, sharply, roughly, is easily reconciled and becomes agreeable and friendly, just as writing on the water soon disappears."
Holding on to anger is bad for us in term of our spiritual practice as well as for our own health. Anger can destroy our merits and cause disharmony. So the longer we hold on to it, the worse it became.
As Buddhists, I believe we all need to learn to be the 3rd type... don't you agree?