This is the first problem I need to work on. Just bought a 7 yr old ex racehorse. She has a tendency to get tired and when I am riding she tries to roll. I don't know what to do about that. I lunge her before I ride her because she is really high strung and hasnt been worked for a while. Is there some sort of tack I could get. I already have to use a martingale because she holds her head too high.