On the Cavalry Commander (10.13-10.14)

And when you notice that high carriage of his neck and lightness of hand give him pleasure, you should not deal hardly with him as though you were forcing him to work, but coax him as when you want to stop[*]; for thus he will break into a fast pace with most confidence.

There is plain proof that a horse takes pleasure in going fast: for when he breaks loose a horse never goes at a walking pace, but always runs. He instinctively takes pleasure in this, provided he is not compelled to run too far for his strength. Nothing in excess is ever pleasing either to horse or man.