Once an apple falls from a tree, does it ever return? Once the bottom of a bucket falls out and all the water goes with it, does the water ever return to the bottomless bucket?
For the moment, let us forget about the big Realization (i.e. enlightenment) and take a much smaller realization. Say you enter a hut in a jungle…where poisonous snakes live. Upon entering you see the room is dimly lit. The door slams shut as someone locks you in from outside. You see what appears to be a snake across the room.
Now, there might be worry and fear about the snake. You might cry out for help due to the fear for your life. Imagine all the thoughts and feelings that might well up in this dire situation. But there is no way out, so you fumble for a flashlight in your pocket. You get it, turn it on, and point the light at the object across the room. You only see a piece of rope on the ground. You clearly see it…for several seconds…and suddenly the flashlight goes out. Perhaps it was the batteries or perhaps a mechanical failure. The question is, do you now fear the shape across the room again? Could you ever lose the realization that it is a piece of rope and suddenly believe it is a snake again?
You clearly saw for only a few seconds, but there is no doubt within you that what you saw was a piece of rope. So, how could the realization be lost? The room is still dimly lit and what you are seeing may no longer be clearly seen. But once you know it is a piece of rope, you will never be fooled by it again.
If the take on a classical Indian analogy is not to your taste, how about a different story….
Say you saw the cups and balls routine performed by a magician. You see balls appear and disappear. You are amazed! How did he do that? So, you delve into the illusion. Perhaps you get some books from the library about sleight of hand and magic tricks…specifically ones that show you how to do the cups and balls routine. You come to realize how the illusion was done…how the magician did it.
Now the question is, could you lose that realization? You realized the secret to the trick…so when you next see a magician perform the cups and balls routine…would it fool you? Even if it has been a long time, wouldn’t seeing the illusion only remind you how it was done? You wouldn’t be fooled by it.
Realization (the big one – enlightenment) is the same way. If you clearly see through the illusions of the mind, then those illusions no longer fool you. Often you may find that encountering the illusion only reinforces the realization of it being only an illusion.
Realization can not be lost. If there was some experience that you think it was Realization, but it goes away….and you find yourself still suffering and being fooled by ego/”me”…then that was not Realization. It was a passing spiritual experience…a glimpse at best, but doubted because it was not clearly seen. Realization is being without doubt (I know it is a rope and not a snake).
There are many kinds of potential spiritual experiences. Some may seem profound, but the effects are minimal or not lasting. It comes down to who/what do you feel yourself to be? As long as there is belief in a personal “me”, you are still being fooled by the illusion. You are taking what is seen and experienced as something that it is not. There is still ignorance. There is still doubt. Only when the ignorance and doubt are no more can it never be lost….only then can it be called Realization.