Through most of history horses were highly prized in China both for their own sakes and as tokens of wealth and strength. In the ancient histories, kingdoms were often measured more in terms of how many horses and chariots they could muster than the size or population of the realm.
This was because China was always threatened and often overrun by irrepressible 'barbarian' hordes thundering out of the steppes and deserts of the north on horseback - Huns, Mongols, Tartars, Manchurians. Emperor Shih Huang Di built the Great Wall around 2,000 years ago to hold them back, but the fate of Chinese dynasties still rested largely on their cavalry. One emperor after another decreed vastly expensive breeding programs to try and improve the quality of their horses, and the silk trade with the West developed largely in order to buy in fresh breeding stock, often from the very enemies against whom the Chinese were trying to defend themselves.
This ancient dependence on the horse for safety explains the Chinese estimation of the creature in daily life. Although riders all around the world take pride in their horses, in China there was traditionally an added dimension to this which fed into the astrological symbol of the Horse.