For a horse frightening situations can occur when you even wouldn’t think of it being so scary. Also guiding your horse into a horse box trailer and out of it can be intimidating. Working in a horse clinic I encountered numerous situations like that. Sometimes just parading in front of the veterinarian was enough for some horses to be frightened and to try to flee.
I like to tell you a great method how to keep horses calm with just a simple horse halter.