7 year old TB mare, never raced, I have had her since she was a weanling. I will cut to the chase - she is FINE to ride at home, quiet for the most part, and very responsive. She has had extensive natural horsemanship ground training, Parelli games, bridleless bareback riding, etc...She is green under saddle as she was just started last year. Started taking her to shows and out trail riding this year. The first couple of months she was great! Went to 3 shows and several trail rides with no incident, then the problems started. She would start out fine and then halfway into the trail ride she would start get nervous and it would just escalate from there to being out of control, rearing, bucking, just extremely upset. She also started kicking other horses if they came anywhere near her, which she never used to do. Same thing at show, but not to that extreme, just nervous and very anxious, hard to control. I can't understand what is provoking this as she was so good for the first few months! She has been checked for lyme, examined for pain, scoped for ulcers, her vision is fine....she has been completely vetted and we can't find anything medically wrong with her to explain this behavior. Does anyone have any other ideas or insight? I feel so frustrated and discouraged and just don't know what to do anymore as the behavior is getting worse every time I take her some where.