Yoga is the cessation of the movements of the consciousness.
I had the unique honor last night of seeing the Sakyong Mipham Rinpoche, the lineage holder of Shambhala Buddhism and hearing him speak. He spoke about the mind being in a constant state of planning, "what's next, what's next after that, and what will come later." "Planning leads to more planning," he said with a smile. His words about planning made me instantly chant the sutra in my head, yogah cittavrtti nirodhah, from Patanjali's Yoga Sutras, Chapter 1 #2. The vrttis is the planning, the never ending thought waves that insist on having an endless inner conversation in our minds. When we take the time, whether in asana, pranayama, meditation or in the shower, to stop the planning we experience the moment without planning our next move. In fact, we enjoy our present moment.
When we stop planning we have an opportunity to see things more clearly within ourselves, which leads to a clearer view of others and the world outside our own vehicle. How many times have you lost your balance while in an asana because you let your mind wander and began a shopping list or a dinner menu? The Sakyong said we often meditate without realizing we are doing so. The word meditate comes from the Tibetan word meaning "to familiarize." When we worry, dwell or rehash an event or emotion over and over again, this is like a negative mantra, but to put a positive spin on this cycle becomes a chore, an act of true tapas and self-discipline to make the change from a negative to a positive. I have noticed in myself that when I can stop this negative cycle (pratipaksabhavanam) then I feel that being truly compassionate towards others is easier, almost natural. When you're happy; I'm happy. When I'm happy; you're happy, etc.
When we practice asanas we familiarize ourselves with our arms, legs, spine, ankle bones, places that were once remote become familiar, that familiarity deepens as our practice deepens. That is why as Iyengar practitioners we begin with the physical form and use the actions of the body to teach us how to stop planning, cease the vrttis long enough to do an asana, take a breath and eventually meditate.