Zat is und order! Sorry. But seriously, Pope Benedict has said that priests must be joyful in a video message to priests attending an internation retreat for priests at Ars for the international year of priests.
"The priest, man of the divine Word and of sacred things, must be today, more than ever, a man of joy and hope," the Holy Father affirmed. "To men who can no longer conceive that God is pure Love, he will always affirm that life is worth living, and that Christ gives it all its meaning because he loves men, all men."
The Pontiff said the patron of parish priests had a "religion of joy," not a "morbid seeking of mortification, as sometimes has been believed."
In that regard, he cited one of St. John Vianney's sayings: "Our happiness is too great, no, no, we will never be able to understand it."
I'll try and smile tomorrow! Translation of the Pope's message here.