The Fly and the Draught-Mule_英语寓言故事

a fly sat on the axle-tree of a chariot, and addressing the
draught-mule said, "how slow you are! why do you not go faster?
see if i do not prick your neck with my sting."
the draught-mule
replied, "i do not heed your threats; i only care for him who
sits above you, and who quickens my pace with his whip, or holds
me back with the reins.
away, therefore, with your insolence,
for i know well when to go fast, and when to go slow."