Usually I'm fine with cantering with no stirrups. I can stay balanced with a light seat and a steady leg. I've never had trouble with it until now.
Recently I started riding a different horse. He's great and I'm already in love with him. He has the most amazing canter. It's energetic and a little speedy but very controllable, and when I ride in half-seat it's literally like flying.
Then today during my lesson, my instructor told me to drop my stirrups. I did, and right away I was unbalanced and flopping all over the place. I almost fell off once, and my instructor let me take my stirrups back. I was shocked and embarased. That has never, ever happened to me before. I tried again and the same thing happened.
Why do you think this happened and what can I do to improve my canter with no stirrups? Is it because it's a different horse and I'm not used to his canter, or is it something else??????
EDIT: Oh, and before it comes up, I know I wasn't hugging with my knees or letting my legs flop around when I was using stirrups. It's a bad habit I once had when I was learning to ride and now I always pay super close attention to that.