hi chloe, my horse is sorta similar to yours, what i would do is before we do anything like trot or canter we would do a lot of halt to backup transitions and then walk to halt work and a lot of circles and then work our way up to a trot and do like trot to walk to back up and trot circles and same thing with the canter. you want to have a connection with your horse and get them listening to you which is the reason for all the transitions is to get their mind working and engaging with what you’re asking. that usually worked for me and lunging them before you ride is very useful too. hope it helped :)
If I were you I would work on a lot of transitions. Doing transitions will help establish control from the rider. When you ride you want to have a partnership with your horse, but you also always want your horse to be listening to you instead of viceversa. Some transitions you can try are, walk to canter, canter to halt, extended trot to a collected sitting trot etc. You can do extended trot along one long side, sitting trot on the short side, collected canter on the other long side, and then back to walk to the other short side.
When asking for downward transitions you also want to make it very clear to your horse what your are asking. For example when you are trying to go down to a trot from your canter make sure you sit down (but don’t drive the horse forward with your seat) give a half half from your knee, pick up your hands, half halt with your hand and clearly say “whoa”. Don’t be afraid to use your voice. If your horse isn’t respecting you, and continues to canter on start to circle with him/ her and slowly make the circle smaller and smaller, your horse will eventually be forced to break down into a trot. If you are reallt being dragged around the ring, the corners and the fence are your friends, if your arms are being pulled out of the sockets and it just seems like you’re horse is going to never stop, don’t be afraid to pull them literally into the fence or the corner.
When she canters then goes back to a trot she’s probably is feeling good and wants to keep going so just talk to her and tell her to ease up a bit
Your horse needs to always feel support so remeber to sit down and keep or lose contact wheter you want to trot or canter.
Raising trot and light contact
Sit down and keep contact.
Hope your question was answered!
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Maybe lunge her a while before you ride to get some of her extra energy out. When you do ride her at a canter try to canter her a long time so she will want to stop.