I simply can not see, and therefore can not ride, a perfectly shaped circle (I'm trying for 20 meter, but this problem is regardless of size). They are most frequently shaped like a "D" although I have been known to throw in several pear shapes in a row. I know the pattern I'm riding is wrong, but it's because I can't visualize where I should be in the arena. Because of this basic problem, it's hard for me to use the circle properly to work on my own body, let alone give the horse the cues she needs to use her body correctly.
Recently, my instructor mentioned in passing that I should put out cones to help with my geometry challenges. This made a lot of sense to me as I did a lot of figure skating as a kid, and spent tons of time using the scribe to sketch out perfect figure 8 circles that I spent hours practicing on. So, I tried the cones during my Saturday morning ride. I started by placing a cone on 4 "points" on the circle: C, X, R, and S. I tried to round out the sides of the circle with 4 additional cones. I mounted my horse near A and rode to the other end of the arena- only to find that my "rounding out" cones were actually bulging out the sides of the circle giving it spiky edges! OK, so I can't even make an intentional circle on the ground, which doesn't bode well for doing this on the horse! I dismounted, fixed the cones, and had a respectable circle laid out with the cones (my instructor confirmed that what looked like a circle to me was in fact a circle).
After warming up, we began riding the posting trot on the circle, and I have to say, it felt amazing, the best I have ever felt on a circle because I was no longer thinking about the shape, I was thinking about riding that shape. My horse was really moving well, and we had no problem with increasing and decreasing the size of the circle (moving inside and outside of the cones) with slight leg pressure.
So, this is a long way of asking, what can I do to work on my own inability to visualize the circle without the cones? How long would you say I can expect to use the cones as a "crutch" before I really internalize what it feels like? (I'm not showing at all, so I don't have a fixed date to work toward. It's just that after seeing how good riding the circle could feel, I want to be able to continue to take advantage of it.)