JillyBean, your advice helped me a lot today! I was riding a new horse, Maddie, who needs a much stronger contact - the difference I felt was huge! - and my instructor had me riding circles centred on X so I had no walls to help me! She was a very forward horse and paid a lot of attention to leg and contact. Riding the circles, I had to keep a strong inside leg and good contact on both reins to keep the shape of the circle. Coming out of canter she had a tendency to fall in, so my instructor had me watching her head: if she glanced to the outside her shoulder was falling in, so I had to correct with my inside rein. Because of everything you've explained to me, I was able to understand the way she was moving much better.
If you believe everything you read, better not read.