Focus on keeping your spine straight. It is the job of the spine to keep the brain alert.
B.K.S. IyengarWe often fool ourselves that we are concentrating because we fix our attention on wavering objects.
B.K.S. IyengarYou know the known, so go a little into the unknown. The mind that is caught up in the known - extended a little beyond reason. The moment you go beyond , you move in the soul. Releasing the bondage of your mind to extend further, reach the unknown a little more. The further you go, you realize that the known is limited and the unknown is vast.
B.K.S. Iyengar