Sleep Vritti Elimination
Of the five chittavritti mento-emotional operations which Patanjali instructed be terminated, the sleep aspect is the most difficult to pin-point. The other four are:
Correct analysis
Incorrect analysis
Imagination
Memory
These four can be disabled by commanding the intellect to cease operations. Of course that is if the intellect is responsive to commands in the first place.
The sleep vritti concerns the kundalini lifeforce such that control of the intellect does not bring the sleep function into a phase where it does not influence the psyche.
One serious problem with Patanjali’s instruction is that he does not state as to how long a yogi would have to suspend the operation of these mento-emotional operations. Srila Yogeshwarananda explained that the time period of suspension should be the time the yogi sets for the meditation session. He said however that is not arbitrarily set. It depends on what the yogi can do in meditation and as to how long he can do so. Some may meditate for five minutes but it has to be meditation as defined by Patanjali. Some other person may meditate for ten or fifty minutes or longer. For the period of meditation the yogi should suspend the operations which Patanjali requires.
There are two ways to tackle the sleep vritti. One is to do asana postures and breath infusion until one is satisfied that all drowsy energy is absent from the psyche. The second method is to do special asanas and/or pranayama as a preliminary step before doing the regular session of asanas and pranayama. This would be done as soon as one begins. One would do this with the intention of removing all drowsy energy. Once that was achieved, one would begin the session for breath infusion.
This can be tested by rising in the early morning, then checking in the physical and subtle bodies for stupor energy. Once the energy is located, one can do postures or breath-infusion to remove it. As soon as one feels that it was removed, one should feel as if the reluctance to wake up and exercise is lifted, as if the psyche developed a positive attitude to early rising.
As for removal of the sleep vritti during meditation. At first one should know how it feels when that energy is not present. Then one should recognize when that energy reclaims the psyche after some meditation is done.