Phantom is a high-strung horse. He was very stressed when brought into the barn and showed signs of that stress. There were times he used to weave so much, he was soaked in sweat. Since the mirror was installed, he has settled down. He has gone through 2 mirrors as he plays with them and ends up breaking a non-breakable mirror. Once that mirror is gone, his bad behavior returned. When I re-installed his mirror, he was a normal horse.
The cost of a mirror isn’t that much and you can install it in minutes. I would recommend that you research the topic and consider a mirror installation. I know of people that have mirrors in their horse trailers to settle down their horses.