Does your horse yank you out of the saddle every few strides?
If you find that happening in the walk and canter, first make sure you’re following the natural forward and back motion of your his head and neck.
You don’t want to block your horse with stiff elbows. If you don’t follow his neck motion by opening and closing your elbows, he might be yanking simply to find a place where he’s comfortable using his neck.
If you find that your contact is elastic and consistent, you can discourage your horse from yanking by tightening your stomach muscles and bracing your back so he can’t pull you forward out of the saddle.
You want to brace your back because when he manages to pull you forward, he gets rewarded for yanking.
If you stay “plugged in” to the saddle with an engaged core, he’ll “hit” your hand and back. That won’t feel comfortable to him so he’ll be discouraged from continuing to yank.