6 years ago, I got my first horse, Destinii. She was a lesson horse and for the first 4 or 5 years, she was great, very little attitude. Just recently, when she moved into another barn with new horses, she became very aggressive. I have done ground training with her, and she walks very obediently, follows me wherever, and she loves parelli. But she is aggressive in the pasture and hasn't bitten yet, but she tosses her head and snaps. I have tried new things with her, like riding without saddle or bridle, but she gives me 'tude and bucks and tosses her head and tries to bite my boots when I move my feet forward to tell her to back up. Also note she is rarely ridden and she used to be ridden regularly. She might be getting spoiled, but can that really make a horse aggressive? I want her to enjoy my presence and have a partnership with her.