In one sense enlightenment is realizing that there is no separate self. The taste of no separate self is totally liberating. But Oneness/enlightenment is not merging. Oneness is when there isnít another. There is no that over there, there is only this. And thatís all there is.
Read here a description of what it feels like to become enlightened, written by Adyashanti, a man who has had such a spiritual awakening:
It is a total waking up outside of time.
This awakening is just like waking up from a dream at night–which is why that metaphor has been used so often throughout the centuries. The dream is as real as this moment. If you think your life is threatened in your dream, youíre going to panic just as much as youíll panic if you think your life is threatened right now. But when you wake up in the morning, you think, ďMy goodness, it wasnít really that real.Ē It was real as dreams go. It existed as dreams exist, but it doesnít have the reality we thought it did when we were in the midst of the dream.
Human beings donít know how significant it is to wake up from a dream in the middle of the night. You literally woke up out of a dimension that you took to be just as true as this dimension. Itís a cataclysmic change of consciousness. Everything that I thought was true in that dream ends up not being true.
When there is a real and authentic spiritual awakening, the impact is exactly the same. Iím not saying this world is or is not a dream–itís pointless to define this world. But I am saying the experience of awakening is exactly like that. Itís the experience of ďMy God, I took myself to be a human being named so-and-so and Iím not. And itís not that Iím something better or bigger or more expansive or more holy or divine. It means Iím not. Period.Ē
When there is awakening to our true nature, our minds are no longer looking at emptiness, because there is no separate somebody to look at it. We realize that the only thing thatís ever looking at emptiness is itself.
There is only this, and as soon as you say what this is, youíve just defined what itís not. This is only realized in the utter demolition of everything that itís not. Then that awakening is an awakening outside of everything that comes and goes.
Enlightenment is a demolition project. It simply shows you that everything you ever believed was true isnít.
This doesnít mean there is not a body. There is obviously a body. There is also a sense of self. Enlightened or not, you will have a sense of self. Otherwise consciousness couldnít work in a body. You can have the experience called a temporary cessation of the experience of self, but I guarantee that it will be temporary because your body cannot function without a sense of self.