Asana offers the opportunity to practice mindfulness. It's pretty simple really. It's not about how deeply into a pose you can go, that is the ego trying to win the game. Yoga is the process of being present with the experience in the moment and yet not attached to the performance. Yoga is watching the experience of the body with the objectivity to allow the experience to be what it is, the awareness focused in the moment of the experience and lastly, being kind and compassionate in the process of the experience.
The tricky part is how you get to this degree of acceptance. The first step is to gather awareness. Drawing the mind to the task of watching the breath helps to cultivate the experience of observing. As the mind becomes more tranquil, flowing with the movement of breath, the body becomes more relaxed, one's Prana (life force) becomes collected and shaped by the pose. The ego is lulled into a state of calmness and receptivity, gradually allowing for the unfolding of smarana, or remembrance, openness and freedom.