Examples of common position mistakes - Wide arms
As you can see Fixed wide arm causes the horses head to come up and for the horse to invert.
All natural movement is blocked as there is no ability for the elbows to be elastic and follow the movement of the horse.
The rider becomes tense across the shoulders which causes stiffness in the body and again restriction for the horse.
You should have elastic elbows that follow the movement of the horse
There should be a line from your elbow, to your hand to the bit