Horses are emotionally intelligent, empathetic creatures. They will usually match the emotions of those around them. Being with a horse in general can lower cortisol levels, and it is no different for the class horse, cortisol being the stress hormone.

You're character has Advantage on Saving Throws against Charm/Fear

Horses have a strong sense of hearing, able to pick up sounds in the 55–33,500 hertz18

range, so they can hear things that humans (who can hear between 20–20,000 hertz) miss

Great Hearing paired with 20/20 Vision gives your character advantage on perception once per day

Horses can see very well, with a nearly 360-degree field of vision, and their eyes are larger than those of any land mammal.

Great Hearing paired with Over 20/20 Vision gives your character advantage on perception once per day

Horses can react surprisingly quickly when they need to, especially since they are prey animals that have to protect themselves. Their reaction time (less than 1 second) is faster than a human’s, which is why you should know where to stand when near a horse to avoid getting hurt if they get spooked or feel threatened.

Add +1 athletics