Help me fix my left hand!

I've had this problem for years, ever since I rode a horse who cut in going to the right and I (wrongly) tried to drag him back out to the rail for months on end. Please don't flame me for that; I know it was wrong and I'm paying for it now!

My problem is this: I ride with my left rein shorter and my left hand higher, stiffer, and without as much give. I've tried lengthening my left rein, but as soon as I think about any other part of my body, my hand drifts back to my hip so I end up with the same tension in the rein as normal - just with worse equitation.

To the left, I'm okay. My horse goes like she's supposed to, canters on the correct lead, everything fine. To the right... I can't give up my outside rein enough to bend her to the inside, or even travel straight. It's killing her right-lead.

I've spent way too long beating myself up mentally about this. I need some new exercise to break this habit. Help?

Carry a riding crop horizontally with both hands between your EVEN reins. Ride around like that until you develop new rein/muscle memory.

I forgot. The other thing you could try is bungee cords. They have to be the correct length, just long enough to hook onto your horse's bit with your arms in the correct position. Ride with those instead of your reins. You have to keep the correct contact or else they fall off. It's a very quick learning curve for obvious reasons! Keep your reins hand tied in a knot as a backup.