The idea that the mind can be trained never occurred to me before I started practicing yoga. The mind and its movements always seemed like something I was at the mercy of. Trains of thoughts crashed into my day, effecting its' entirety; dictating for me the kind of day I was going to have. The funny thing is that I had trained my mind as a kid. You kmow when you lay down to go to sleep you give your mind the chance to run free? Sometimes whether you like it or not. If it's particularly active you can't sleep. I sang to myself to counteract that problem. I would hear songs I liked in my mind, trying to hear them as exact as possible. I practiced at this (without knowing that I was) so much that even to this day my mind chooses songs it thinks appropriate to situations I find myself in.
Pratyahara is the withdrawal of the senses. As I mentioned last week, we are both physical and nonphysical, and we have a hard time experiencing the non because we identify so closely with the physical. It may seem counterintuitive to practice asana to draw our attention from the physical, but our mental processes are ceaseless and, as I'm sure you've noticed, your mind reacts to asana; you experience emotions that cause more thoughts. It's this process that I'd like you to focus on. Not to get caught up and carried away, but to notice the patterns in your own personal mental processes. The more familiar you become with them, the more you can change them, beginning to control the flow of your thoughts, instead of being at their mercy.