I believe that in Iyengar Yoga as in any spiritual practices the joy and peace come from letting go of the idea of the ego-doer.
There is no certified path to enlightenment, liberation peace of mind, or samadhi.
And if someone gets trapped in the doing, doing, doing, thinking that will certainly lead to a goal well the only result will be frustration and more doing instead of being, in the attempt of controlling but nobody can control his life, at best we can live it fully and embrace it.
Of course there are masters, activities, readings and places that are more suitable for a spiritual seeker but that it is all.
The journey is inward the path is awareness, surrender and be able to just be always fully present in each moment observing, experiencing the flow of life. But not being caught in to it, not being caught into the wish, the illusion of controlling it.
In the present there is nothing to be controlled. It is only in the idea of future and past that control exists and that is an illusion as life it is never in the past nor in the future.
I think that in yoga while practicing, adjustment should be made moment to moment into the present, in the attempt to be into to the asana and not with the goal of reaching a perfect asana into the future, next moment, hours, week...
Practice it is about being fully aware of your self as a whole into the present at each breath and if the mind moves to do a posture for the future that is when the concentration fail...
It is the same in living when one is not fully present with its whole self then he or she is not living.
And now let us open our mat and start practice!