If we refer to Advaita, there are three states of consciousness, namely waking, deep sleep and dreaming, also covered by the fourth state which is described as pure consciousness, the background that transcends these three common states of consciousness. The first state is the one we experience in the day when we are awake and conscious to be alive and acting. The second state is of profound sleep, the one we experience immediately when we fall asleep. This state is characterized by a total lack of consciousness. In the third one, the paradoxical sleep, we experience dreams. The fourth state of consciousness is the one which covers the first three states, which is also called the Self.
What happens when we fall asleep? We reach the profound sleep, in which we forget everything, nothing of our personality remains of what we were during the day. In other terms, falling asleep is reaching a state of total forgetfulness. Looking at it from the opposite side, from the subconscious mind that runs all our activities, the one who doesn’t want to forget will never fall asleep, because if he falls asleep, he will understand that nothing he was worrying about was important, as it is indeed possible to forget it all. The subconscious strategy will demand not to forget, not to cease to worry about, and hence not to fall asleep.
In fact, in this kind of situation, forgetfulness means mainly forgiveness.
When sleeplessness is settled in the organism for long, forgetting or forgiving may not be sufficient to recover a good sleep, because sleeplessness may have become a pattern that is triggered by any tiny issue that arises in one’s life, since it was so far the most common way to address anything that threatens the subconscious mind.
A good exercise to avoid sleeplessness during the night is to observe, whenever an awakening appears, the tendency to say no to whatever raises. For instance regarding the position to adopt, in order to rapidly come back to the sleep, or regarding some thoughts or subject to think about, that may appear relevant to think or not, etc. As long as there is some “no” that is expressed, as long as some spontaneous behavior is rejected by some inner assessment that that should not arrive, there is an inner disagreement that will lead the sleep to be, unconsciously, banned. Then, the only way is to observe, notice, bring peace and surrender.