Narcissists feel empty inside due to extreme emotional neglect. They were never seen or mirrored for who they authentically were. Every time they expressed an authentic part of themselves, they were either shamed, ignored, ridiculed or attacked. Eventually, their True Self, at first gushing with life, dried up. This brought them face-to-face with death, with the abyss inside. Nobody can connect with someone who is dead inside. So the narcissist created a false self, which was fuelled by their imagination. That is, the narcissist dissociated from reality and dwelled in a fantasy-induced world.
The reason a narcissist flip-flops between wanting you and not wanting you is because you are a part of that fantasy-induced world.
Because the narcissist was treated like a sub-human, they internalised an agonising sense of being inherently flawed. Their false self was not only a solution for a feeling of emptiness, it was the solution for irredeemable inferiority. The narcissist therefore uses their imagination to create an alternative self which is energised and special. In order to maintain this false reality, anything the narcissist allows into their world must also be special.
Alas, a flawed human being can let the narcissist down. So they imagined you to be perfect, and idealised you as someone who would love and accept them unconditionally while showing no flaws. With that hidden contract signed, they permitted you access pass into their world.
The problem is that you are not ideal and perfect; you are human.Eventually, reality always asserts itself in the narcissist’s fantasy world. As hard as you try to please the narcissist, you will always let them down.Nobody can live up to the narcissist’s grandiose, and frankly, insane expectations.
The narcissist’s flip-flopping is the outer manifestation of their internal struggle to maintain you as the ideal and perfect person in their life. The key is not to understand the narcissist’s inner process, but rather to understand that you are not real to the narcissist. You are a figment of their imagination, which has been plastered over the real you. The sooner you accept this and detach yourself from the narcissist, the better.