Try to keep your eyes alert and open, tt is preferable to avoid closing them because you will probably find it quite difficult not to fall asleep, which is definitely not the point of the exercise!
During your daily 20-minute session try and give yourself the time to practise some sharp, Long hair layered haircuts for round faces well directed thoughts to avoid your mind from wandering and spreading out, covering other possible important issues.This session can also encourage you to put into practice your excellent skills of observation. A good practice is to go over the primary directions, and to notice if you are aware of any tension in your body and to address it without trying to correct it.That is the secret of success.
Books are used to support the head. If you have too many, how-even your chin will drop and you will feel pressure on your throat.