it is a mental construct
Good explanation of what self-consciousness attempts to do:
Self-consciousness is not something obviously "self-existing" it is a fiction, - it is ungrounded because it is - a mental construct.
Rather than being selfsufficient, - consciousness is like the surface of the sea: dependent on unknown depths ("conditions," as the Buddha called them) that it cannot grasp - because it is a manifestation of them.
The problem arises because this conditioned, and therefore unstable, consciousness wants to - ground itself, to make itself real.
But to real-ize itself is to objectify itself - meaning to grasp itself, since an object is that-which-is-grasped.
The ego-self is this continuing attempt to objectify oneself by grasping oneself, something we can no more do than a hand can grasp itself.