It was a little while before I really understood what is essentially a maxim for all riders. Hunter and jumper riders know well the saying, "throw your heart over the fence and the horse will follow." When I was jumping I kept that in mind, since I knew if I looked at the ground in front of the fence I would end up laying on it.
It's a physical thing. We've been balancing on our two feet for a number of years by now, and don't give it much conscious thought. We look in the direction we intend to go and shift our balance accordingly. When we ride, that shift affects the horse's balance far more dramatically due to our center of gravity being higher than the horse's.
Funny that an action as innocuous as looking at something can set your course with such certainty. And you know what? I've learned more magical things about direction of gaze, too. I've learned that if something is scary, you're far better off if you concentrate your vision on where you're intending on going than the terrifying object. I've learned if you stop looking, you lose track of what's happening to your horse, and that starts a snowball of frustration rolling down hill.
I've learned to apply this little technique to the aspects of my life that are separate from what I try to accomplish in the saddle. It goes hand in hand with having a goal--kind of like a support technique. You just have to be careful to look where you want to go, because you'll surely go where you look.