We tend to take a wrong body as our true body. We think our eyes, ears, nose and so on are our body. But Buddhism tells us they are not our true body. Taking them as our true body is like (in a Chinese saying) taking a thief as your father. Or we say it is like adding an extra head to the head.
When I do the sitting meditation, sometimes I close my eyes and try to imagine if I lose sight (which is kind of a real threat to me. I used to have nightmares that my eyes become very dry and I lost my sight.). When I am blind, a lot of things and values I have regarded as important are not important to me anymore. I then ask, am I different or am I the same. Then I try to imagine what if I lose my hearing. Am I the same? Am I different? How about losing my touch? Am I the same? Am I different?
In Buddhism, we say see with your whole body. Use your ears to look. Use your eyes to hear. Then you can see with your whole body.
Our brain tends to interpret our sensation. When we see the apple, our brain will interpret my eyes see the apple. But when your brain interprets, you are already too slow. Before the concept of eyes and apple arise, you already see. So see with your whole body. See with your whole being. When your whole body sees a leaf falling, your whole being knows that the Fall is coming. When your whole body sees grass growing, your whole being knows that Spring is coming. Such knowing (or not knowing) is before the world of language.
In sutra, Buddha gave an example. He said when there is light, you see. When it is totally dark, you also see. You see darkness. Such seeing is using your whole body to see.
When you are lost in your thoughts, you are not seeing. When you notice you are thinking, you are seeing.
This true body is the body we will never lose, and it never changes. It is the universal substance that we share with the universe. Or we call it emptiness. Buddhism practice is to be familiar with your true body. It is the source of our origin. Being with your source brings you the true peace.
For techniques to help you see with your whole body, many know of breathing technique. Try to feel the flow of air through your nose to your abdomen. Try to breath naturally, which is very easy to do if you can sit straight and still. Get your attention off your brain.
Another technique is to focus on listening to the sounds. Try to listen to all the sounds together, close and very far away. Try to see how much you can hear maximally. In Chinese, we say that ears are clear and quiet. They are not like eyes, which often distract us. When we hear things, we often hear sounds rising and falling. It happens fast. So it is easy to see the impermanence of it. But when we see things, we tend to think those things will stay there. Also it seems that optical nerves are directly connected to concept/image in the brain, and thus easy to be distractive.
Once you are awake, please always keep your eyes open and always seeing.