One common misconception that many people make is that when they close their eyes, they are experiencing total darkness.
The truth is that you are actually seeing the back of your eyelids. It only appears to be total darkness at first, because your eyelids immediately cut off all light and the cones and rods in your eyes have not adjusted to the darkness yet.
However, if you stay patient and wait, you'll notice that you begin to see more than just darkness. You begin to see that you can adjust your point of reference so that you are looking further in the distance.
The practice of distance focusing is a technique that utilizes your ability to focus your eyes on a point that is further than an object that is right in front of you. You may have even done this before with those popular tricky 3D images where it looks like an ordinary image, but if you look past the image, you can see a 3D boat or object take shape.
It's this same focus adjustment technique that can be used for falling asleep, but instead you do it with your eyes closed.
Distance Focusing (Step-By-Step):
Turn off or dim the lights. Remove all noise distractions from the bedroom.
Climb into bed and close your eyes.
As you are lying in bed, become fully aware that the darkness you are seeing is actually the back of your eyelids.
Begin to change your depth of focus to a point that is further away.
When you are able to successfully do this, you will see a definite shift in your visual perception of the darkness.
A more serene darkness becomes visible, rather than the immediate darkness from looking close up.
Continue focusing into the distant darkness and experiencing whatever images appear there.
Eventually this peaceful darkness will lull your mind to state of sleep.