Stress Your horse has stress. New ulcer statistics are much higher than previously thought. A domestic horse is living an unnatural life so we do all we can to try to mimic their life in the wild, which is impossible, of course.
Most behavioral issues in horses are caused by pain. Seriously open your mind to that. Maybe the vet has come and said he couldn’t find anything. Maybe you just had your saddle fitted. Maybe a training video suggested that bit. Your horse’s opinion matters when it comes to pain. Listen to his calming signals because we can train horses to hide their pain but it’s always a bad idea.