“A monk decides to meditate alone.
Away from his monastery, he takes a boat and goes to the middle of the lake, closes his eyes and begins to meditate.
After a few hours of unperturbed silence,
he suddenly feels the blow of another boat hitting his.  With his eyes still closed, he feels his anger rising and, when he opens his eyes, he is ready to shout at the boatman who dared to disturb his meditation.
But when he opened his eyes,
saw that it was an empty boat, not tied up, floating in the middle of the lake …

At that moment, the monk achieves self-realization and understands that anger is within him;
it simply needs to hit an external object to provoke it.

After that, whenever he meets someone who irritates or provokes his anger, he remembers;
the other person is just an empty boat.
Anger is inside me.  ”

Thich Nhat Hanh