Disability often comes with a massive rearranging of identity, even when there's little or no change to one's physical appearance. For Anakin this coincided with the absolute shattering of his identity that was 1. Operation Knightfall and 2. Mustafar, and with the reforging of one's identity traditional of Sith apprentices. To further disrupt his prior identity, he now essentially has two bodies- the metal monster seen by the outside world, and the injured remnants of his organic body spending so much time in bacta.
So, like with any radical alteration of identity, there's going to be an inevitable transition phase, which may be long or short, and I'm willing to bet his definitely lasted longer than initially recovering from surgery and physically adapting to the suit.
It's no wonder he no longer sees himself as human, especially since Palpatine had total control over his entire transition phase. That's... well, so there are certain psychological effects of abuse that almost exclusively happen to children because adults who endure the same mistreatment already have a formed identity. But the identity of an adult can still be disrupted or even dissolved in various ways. And one common model of the process of indoctrination into a cult is that a person's previous identity and worldview are systemically "unfrozen", molded to fit the cult, and then "refrozen." The Sith are generally thought of as a cult.
The fact that he can even remember Anakin Skywalker at all, let alone still be him, and eventually shoulder the guilt well enough to come back to the light- just, Jesus fucking Christ. Pals, I could not.
