One of the biggest differences between humans and horses is that the human is an omnivore and a predator. 
Reviewing the evolution of the human, which is not as old as the evolution of the horse, the human evolved from a hunter and collector to a farmer.RobertAndCelineThe fact that we were hunters, (and with that predators), is clearly visible for the horse. The human’s eyes are placed close together so we are able to focus on prey. Even our movements are very similar to those of other predators.

The very first contact horses had with humans was being preyed. Only later the human used the power and speed of the horse to its own advantage. 
The horse enabled the human to travel faster and longer distances with more baggage. Without the horse, human civilization probably wouldn't have spread as fast and wide.

Considering the horse is a flight animal that is born and evolved to live on the open range. It was designed to survive without humans and in complete freedom. And yet, humans used the horse even as a weapon to fight other humans. 

 One can only imagine how much a horse has to trust a Human to fight other two-legged predators together. That naivety of the horse puts a huge responsibility on the shoulders of a true horseman. The responsibility to not shame this blind trust of the prey animal horse. A responsibility that has to be taken very seriously.wildHorses2a

In fact, this naivety of the Horse can help - for example with a psychologically traumatized horse.  If the right and honest horsemanship is applied, the horse can overcome his trauma way much faster than compared to many humans having the same problem.  A horse will always opt for survival and is thereby dependent on his intelligence and ability to assess.

It is our responsibility as humans to honor and care for the horse using their abilities the best way we know-how.