(I apologise in advance for the lengthy explanation, and I hope this is the right section)
So I have a 5 year old AQH mare who I trained myself and she is doing really well. She respects me on the ground and is an absolute dream while I am riding her, but recently I have discovered a wierd quirk of hers and Im not sure how to handle it. My uncle recently purchased a round pen and placed it inside of his pasture. His pasture is right next to mine and to get to the pen you have to walk down a gently slopeing hill. He aggreed to let me use it so naturally I was very excited. I tool my mare into his pasture and started walking her down the hill when she suddenly started acting up. It really surprised me because she is usually very well mannered. She didn't want to walk foreward and when I finally got her to move she would dart foreward and almost knocked me over. I had to fight her the whole way down the hill and once I reached the flat part near the pen she was fine. I walked her around and shrugged it off as her getting spooked by something or being afraid of the new pasture. I lunged her for about 30 minutes and then let her walk so she could cool down before I took her back to her pasture. On the way back up she didn't act up and everything was great.
The next day I took her on a trail ride around the farm. She was acting really hyper and wanting to run so after ten minutes of trying to hold her back I decided to go ahead and lunge her. I rode her into my uncle's pasture and started down the hill. She imediatly started acting up and didn't want to go down the hill. She balked up and no matter how much I encouraged her she would not go down that hill. I ended up having to get up and try to walk her down the hill. She continued to act up and once I got her down the hill she was fine again...
This has happened repeatedly and Im not really sure whats going on. I would really like to be able to lunge her in the round pen without having to fight her down the hill. Im afraid I will get hurt if this continues so I have stopped trying to get down there for now. I have tried everything I can think of to get her over this fear. Does anyone have any suggestions on how I can get her over her fear or whats causing it?