So I have a very frustrating, potentially dangerous problem. My horse, Ace, is very well mannered and laid back 98% of the time. He'll just go along with whatever you want him to do. It's the 2% that worries me. He is herd bound; he's gotten much better since I got him, and he truly does enjoy spending time with me, but sometimes his herdboundness shows through, severely. Today, for example. I was getting my senior pictures done, so I groomed him about 2 hours before then put him in a stall. The other four horses were out in the pasture. I went back out to get him; he was a little nervous, but not too bad. He did alright for the pictures, but he tossed his head a lot and pranced around. (He usually doesn't bat an eye and stands like a rock, except maybe wanting to eat grass.) I then took him to a soft, grassy spot, and before I knew he was down and rolling. The rope got away from me, and when he got up, before I could get him, he took off tearing across the yard to get to the others. Well then they all got running, and he was running outside of the pasture alongside the others along the highway. Cars were slowing and stopping everywhere; thankfully he never got in the road, but he was close. He came racing back, then made it back to the barn where my sister caught him and he was fine after that, but it scared us all. This was not the first incident like this. Back when I made the stupid mistake (and I have learned from it) of lunging him in a not enclosed area, whenever I would toss the rope at him to go faster, sometimes it would freak him out and he would get away from me and go running, always to get to the others. That happened about three times. Also when he spooks he has a tendency to bolt (which thankfully doesn't happen very often) and he runs to be with another horse. All of this actually really surprises me. Like I said, normally he's nothing like this, but certain situations just set him off, and it's hard for me to tell when it's coming. It all just happens so fast and then he's gone, and I can't control him. I really have no idea how to fix this, if it even can be fixed. I don't want him or anyone getting hurt. Any ideas?