Horse-racing enthusiasts like to say that the jockey accounts for 10 percent of a horse's performance on any given day. While that's hardly scientific, it gets to the point of a jockey's role: He can't do much with a lousy horse, but he can help a great horse win. The top jockey's will have a good judge of pace, be well positioned and have a knowledgeable feel for the horse. Knowing "what your horse has left in the tank" is somewhat very important in the finishing stages of a race. Some horses prefer to hang back and break at the last minute, while others, known as speed horses, like to be out front the whole time. Some horses are comfortable running in close quarters and some are easily intimidated. A jockey should take these factors into account and adjust his riding accordingly.
Good jockeys study form. They review footage of, not only their mount but that of their opposition, updates on their performances and running strategy. eg* If three speed horses are entering your race, you might want to let them battle it out for the frontrunner position and surge once they tire. Jockeys also need to know the track. For example, where is the better going?
Jockeys also have very particular physical characteristics. Controlling a horse at +60km per hour requires a rare combination of strength and technique. Jockeys weigh between 48 and 54 kgs and monitor their diets very closely. Finally, the best jockeys can relate to horses—they know how to keep them calm in tense race situations, saving their energy for where it matters.