If you look up "Nirvana" - you'll see a literal translation of Annihilation. What does this mean? Annihilate what? What is annihilated?
The process called neti-neti is negation - watching all that arises without judgement, without labelling, a silent awareness of what is arising, including thoughts, beliefs, the mechanism of the mind, witnessing bodily sensations, including those which seem to tie in thought in the form of emotion, heaviness in the chest, tension in the head or face, etc.
In the process of negation - negating everything that arises, everything that is known, we come to this body-mind. Thoughts arise, the form of the body appears, seeking, getting this, not getting it, understanding, peace, love, God, enlightenment, gurus, "I have a good intellectual understanding but I'm not there yet", resistance, non-resistance.... it all arises and is negated as NOT WHAT I AM.
Negation is NOT resistance - if a thought appears "I don't understand" or "I'm not yet enlightened" or "I have so far to go before I get this" - that's perfectly fine as it is. The point is to WITNESS it. See how thoughts create beliefs, how thoughts are identified with. SEE how thoughts create this identity, see how thoughts create this sense of self. SEE that this "I" is created NOW in thought only, "I" is just a presently-arising thought. Does this "I" have any more substance that that? "I" points to this false self, this "person" who has a body, a mind, a life story.
Yet that sense of "I AM" is undeniable - I exist, I know.... there is an undeniable consciousness OF the world, OF this body-mind - a silent WATCHING going on all the time, IMPERSONAL, with no flavor of the individual, no form, no shape, no smell, no taste... just a silent witnessing going on in the immediacy of NOW, just a reflection of the world in this knowing.
We've identified this sense of "I" or "I AM" with the body-mind. That's the basic error, the false self. This sense of "I AM" is an expression of what you truly are - that silent impersonal seeing/knowing/awareness/beingness that is undeniable and totally present NOW - BEFORE, during and after any seeking takes place.
Seeking is looking in the wrong direction - looking to make the mind something different, looking to gain an experience of bliss or peace or light. This is 100% missing the point.
Our sense of self, our identity or individuality, our ego, our life story, our identification with the "person" or separately existing entity within that body-mind - THAT is what is annihilated. Nirvana or enlightenment or whatever label you want, is simply the extinguishing of identification with that false sense of self and knowing NOW that what you are is that silent space of knowing, that simple ordinary awareness which sees/knows all that arises.
And this causes great fear for the mind - what would I BE without this story? What would happen if I no longer WAS this person? Would I lose my family or house or job or personality - would I lose my mind? So this is a scary proposition - annihilation is totally losing every single thing you have and ARE (or BELIEVE you are.) We believe we ARE this person and HAVE these things. Annihilation is 100% seeing through of these beliefs.
So this body-mind, the life story, seeking, getting this or not getting this, every single form and aspect of the life story and person that you have taken yourself to be is FALSE. Realization or liberation is the annihilation of the IDENTIFICATION with this false arising form and realizing that you are the simple knowing presence, fully present NOW.
It may seem that seeking is required, some sort of path or process, like meditation or mantra or satsang or reading... or it may just spontaneously dawn that what arises is ALWAYS temporary - what you are is the awareness in which any of it arises. Seeking is happening - it's perfectly fine. Don't try to stop seeking, that's just more mind. Let go of the need to become anything and rest in what you already are. Just witness the mind without resistance - let it be. What you are is beyond the "thinker".
This is the pathless path - the realization that there is absolutely nothing to realize - what you are is nothing you could possibly perceive or conceive of. What you are is the very perception itself. And in this perception of the world, it is known that anything that arises is either not what I am OR I am EVERYTHING that arises (which is really the same thing). Neither one of these could BE if you're a separate person.
Annihilation is not possible unless you're willing to give up everything, including your own self that you take yourself to be. And in this giving up and resting in the nothingness that you are, you find you gain the entire world.