I have a thoroughbred who likes to go fast in the flat and jumping, she will get flustered and work herself up to the point where she sometimes bucks. Do you have tips?

Gymnastics, grids with poles before and after jumps. Get the horse thinking. I agree with canter poles set as a 5 stride. Do the poles in 5 strides, shorten strides to 6 strides, optional to do 4 strides but I wouldn't recommend that with a horse who is already rushing jumps.
My horse used to go galloping round courses and on the flat and didn’t really have a canter transition it was walk ,trot , gallop and now he has a lovely canter most of the time . Wat really helped was poles working on getting a distance between them for example one time get 5 strides the next get 6 then 7 and add loads of circles before and after and this will really get him thinking about what u r asking him for .poles are the best as he really has to think where his feet r going and when practising jumping put a few poles before the jump so he slows it up to think about wat he’s doing . Hope this helped 😁
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