This technique should be done when you are ready to fall asleep, not when you are supposed to sleep or at the time prescribed to you. When your body actually says it is ready, do this meditation.
Just rest and wait passively, that’s all!
Don’t try to sleep.
Don’t try to follow any method to fall asleep. Don’t feel guilty or anxious if sleep is not happening to you.
While waiting you will always be more aware. When you are passively waiting, you will be more aware. If you are aggressive, you will not have awareness.
Understand one important thing: the more passive and receptive you are, the more your awareness will increase. That is why prayer develops your awareness. During prayer you are very passive, deep, waiting for the grace. A prayerful or passive mood will bring you to awareness. Just be in a passive mood. You can even think of sleep as a goddess. In the Upanishad we have a chant to respect or worship the deity of sleep or nidra devi! You can think of sushupti or the deep-sleep state as a goddess. Wait with a passive mood for Her to land on you and bless you. Just be in a deep, waiting mood.
Suddenly you will see that you are slowly losing the awareness about your body but you are still aware. You will not lose the idea ‘I’. Be aware of that moment. The door for the fourth state, samadhi, spiritually awakened state, will open. In that space your verbalization will not be active. You will not have thoughts but you will have consciousness, ‘I am not aware of my body but I am aware that I exist.’
At this point suddenly you will see that you are completely relaxed, you are aware, but the idea of the body doesn’t exist. The following morning you will see that you are fresh, alive! But you will feel you were aware throughout the night. You never lost your awareness, yet you feel completely rested and relaxed. You don’t feel any tiredness. This is the experience if you have had the glimpse of the samadhi state.
source: Living Enlightenment