Horse Riding - Tension in the hindquarter yield

If the horse gets tense and wants to rush away from your leg, first think about the amount of pressure you are using, maybe you need to use less. If you are using a light pressure and the horse is still tense and rushing then try the following:
Flex the horse into neutral, then plant your fist on your leg so that you can keep the horse flexed if it gets tense and wants to straighten out.
Slide your leg back and ask the hindquarters to move with a light pressure.
Then Instead of immediately taking your leg off, leave your leg on the horse, as it spins its hindquarters around. It may do a couple of circles before it starts to slow.
When the horse starts to slow, (it will!) take the pressure off so that the leg is just resting on the horse, then wait for the horse to stand still with flexion.
Repeat. This time it should take less time for the horse to slow. Again take the pressure off and wait for the horse to stand in flexion. Repeat until the horse is less reactive about your leg... we are desensitizing the horse to our leg. Usually we need to do the opposite, but some horses with big flight responses or histories of trauma can be worried about this. If you have done a good job on the ground, with moving the hindquarters from pressure, and rubbing them at the end, then you might find this problem has resolved itself by the time you get in the saddle. However this is not always the case,as some horses have had excessive spurring in the past.
Repeat until the horse does not worry about your leg. When the horse is no longer worried and trying to escape the leg, they will usually offer a slower step from the beginning. Click and treat. Repeat.
When the horse can offer one slow relaxed step, then progress to increasing the number of steps.
It is much harder to teach the horse to do one good step than it is to get them to rush around.