After Bankei had passed away, a blind man who lived near the master's temple told a friend:
"Since I am blind, I cannot watch a person's face, so I must judge his character by the sound of his voice. Ordinarily when I hear someone congratulate another upon his happiness or success, I also hear a secret tone of envy. When condolence is expressed for the misfortune of another, I hear pleasure and satisfaction, as if the one condoling was really glad there was something left to gain in his own world.
"In all my experience, however, Bankei's voice was always sincere. Whenever he expressed happiness, I heard nothing but happiness, and whenever he expressed sorrow, sorrow was all I heard."
For further Zen koans, consult for example; http://www.ashidakim.com/zenkoans/
"Your joy is your sorrow unmasked. And the selfsame well from which your laughter rises was oftentimes filled with your tears. And how else can it be? The deeper that sorrow carves into your being, the more joy you can contain." -Kahlil Gibran