The phrase "dulce est desipere in loco" comes from Horace, Odes
4.12.28, and means "It's pleasant to act crazy on occasion." Herodotus puts these words into the mouth of the Egyptian king Amasis (2.173.3-4, tr. George Rawlinson):
Bowmen bend their bows when they wish to shoot; unbrace them when the shooting is over. Were they kept always strung they would break, and fail the archer in time of need. So it is with men. If they give themselves constantly to serious work, and never indulge awhile in pastime or sport, they lose their senses, and become mad or moody. Knowing this, I divide my life between pastime and business.