Taking a dog works wonders. They feel protected by their pet predator.
Depending on how calm and responsible your dog is (if you have one), bringing dogs out on trails has always been beneficial for my trail riding experiences, it would always calm my horse down, but make sure that if it’s long distance that you have proper equipment to give your dog food, water, etc.
Try riding with one other horse, slowly creating distance between you. Have the other horse go ahead or behind on the trail, and then come back to your horse. Increase this distance until they are comfortable being by themselves