Derealization did once hit me in a really bad phase of Insomnia. It's not something that can be half-present, or guessable, but downright troubling and strange like nothing else. There's a sudden wall between you and the world. You know it's not real, but if there were three aspects to make up your perception of people, it's two now. A world reduced into 2D. Wrong. Creepy. Inexplainable