Alistair MacLean quotes a story about John Tauber, the German mystic of the 13th Century.
One day John Tauber met a beggar. "God give you a good day, my friend," he said. The begger answered, "I thank God I have never had a bad one." Then Tauber said, "God give you a happy life, my friend." "I thank God," replied the beggar, "I am never unhappy."
An amazed Tauber said, "What do you mean every day is a good one, and every day is a happy one." "Well," said the beggar, "when it is fine I thank God, when it rains I thank God. When I have plenty I thank God, when I am hungry I thank God. Since God's will is my will, whatever pleases Him pleases me."
Tauber looked at the man in astonishment. "Who are you?" he said. "I am a king," replied the beggar. "And where is your kingdom, Tauber asked?"
"It is in my heart", the beggar replied.
