I have limited experience with horses, but enough to know that they were pretty much the boss. After falling off into a thick patch of goat heads, I was even less a fan.
My dad was raised on a farm, and worked horses until they got a tractor in the mid 30's. He told stories about his horse; riding it to school when he was in grade school; friends with skittish horses, etc. One time when I was maybe 10 years old, I made the comment "It must have been fun in those days, working and riding horses all the time".
His reply "Hell no! Horses are dumb, unpredictable, and a lot of work. If you aren't smarter, they will kill you or mess you up! Tractors are the best thing that ever happened to farming!".
Come to think of it, the old daily paper in this town used to re-publish editions from early statehood; made interesting reading...and it seemed like every edition had something about a resident being killed or injured by a horse falling with them, kicking them, or otherwise involved in some kind of accident.