I may be made the victim of a practical joke and get angry, but if I can objectively realize the joke of it and laugh with others, my anger will be dissolved before I am aware of it, as if it were secretly replaced. To realize is to objectify. The more advanced the degree of objectification, the more complete is the dissolution of internal pressure. Internal pressure is ego, and laughter is the cancellation of ego. In fact, there are no such entities as what we call ego, consciousness, and so on: all derive from the successive manifestations of internal pressure.
From Zen Training: Methods and Philosophy by Katsuki Sekida, page 150