Good question @HisServant about sunn. I also am suffering from the same confusion as it happens quite frequently with me as of late. Although I do like to do simran when lying down as body is most comfortable in that position so I can focus purely on the mantar rather than being distracted by uncomfortable body aches. Never the less if I meditate on the train on the way to work in a seated position I also tend to loose awareness for a few minutes at a time.
Here is something I read in favour of both approaches,. which doesn't make choosing a path to explore any easier. My concern is that lets say we force ourselves to remain aware as we drift into a meditation state. Unless shabad of some kinds is pargat or doesn't become pargat. We will wonder without an anchor point. Everything I have heard to date suggests shabad must be the focal point of the journey inwards.
Japing until you fall asleep/sunn:
Whenever I teach a beginning meditation course, I talk about the relationship between meditating and falling asleep, for, as you have discovered, they are more closely related than you might think. And certainly closer than we want them to be!
We tend to think of the three states of consciousness – subconscious sleep, waking consciousness, and superconscious meditation – as linear, with “sub” and “super” nicely separated by the waking state.
In fact, all three meet at what you might call the horizon line of awareness.
Meditating and sleep also share certain characteristics. Both involve the cessation of physical action, mental activity, and sensory input. The all-important difference between them is that to enter superconsciousness requires an increase of energy, whereas to enter subconsciousness requires a decrease.
We go to sleep when our energy has run out. If we are filled with energy — mental or physical — we can’t enter subconsciousness, but have to do something with all that energy before sleep will come.
One of the challenges of meditation is to learn how to increase our energy in a non-physical, non-mental, totally relaxed way. At first this seems impossible, but gradually we learn. For all the energy we need is already within us. It is a matter of learning how to direct it.
Another obstacle to entering superconsciousness is that we already have a fixed habit of what to do when we withdraw our energy from body, mind, and senses: we go to sleep.
What is happening to you (which is common) is that, finding yourself with your energy withdrawn you naturally go where you are accustomed to going, which is sleep, not meditation.
The key to breaking that cycle is the concentrated application of will power and energy, which makes sleep impossible. Naturally, this takes time to learn.
In meditation classes, I draw a diagram to illustrate this point. I’ll try to explain it in words here and hope you can see what I mean.
Think of a capital Y. Now imagine that Y is lying on its side, with the single straight line pointing to the left (as you look at it) and the V opening to the right.
The leftmost point of that straight line is waking consciousness. When you decide to sleep or to meditate, you travel along that straight line, to the right, closing down as you go all your usual expressions of energy – talking, moving, thinking, hearing, seeing, tasting, feeling, etc. – until you reach the intersection where the V meets the straight line.
At that point, you have a choice to make. If you continue to decrease your energy, you fall into subconscious sleep. If, however, at that point, through devotion, techniques, concentration, willpower, etc., you increase your energy instead, you go into superconsciousness.
It’s like watching a movie. When you watch a great movie it is easy to be fully concentrated on it and be full of energy, but if the movie is boring and uninteresting, it’s easy to lose focus and feel sleepy.
If during the course of your meditation, your energy decreases, you sink back past that junction until you find yourself suddenly on the “low road,” not meditating at all, but dreaming and sleeping.
The solution is simple. When you find yourself suddenly subconscious, increase your energy through any one of the many methods you have to draw upon in Kriya Yoga or whatever path to Self-realization you are following.
Eventually, you will create a superconscious habit stronger than your subconscious habit, and this will cease to be a problem for you.
Another form of guidance I read was do bakhari bani until you notice that you speech is becoming less clear, distorted or incomplete. This is the time that one is approaching the sleep juncture. At this point one needs to build more focused concentration on the mantar so that you slip through into mediation and not fall into sleep. The posting I read suggested this would lead to the next level of astral awareness.
I only once ever recall this happening to me when my surti awoke in a dark place, wondering where I had come. I guess this was the goal all along but I didn't realise it at the time and no one pointed it out to me clearly afterwards.