Try to stay relaxed and try bare back
also don’t grip with your thighs...sometimes i catch myself doing that
think about moving your hips in a circular motion, push through your heels, and stay relaxed. don’t tense up, that doesn’t help. move with the horse.
Do core (abs, back and obliques) exercises at home to help strengthen the muscles you need to move with your horse. Also bareback helps
I tried bareback and it helped me move with my horse and sit the canter better, amazing too