There's a characteristically brilliant Peanuts strip which opens with Linus sitting on the living room floor, anxiously clutching his mouth. Lucy enters and asks what's wrong. "I'm aware of my tongue," he explains. "It's an awful feeling! Every now and then I become aware that I have a tongue inside my mouth, and then it starts to feel lumped up ... I can't help it ... I can't put it out of my mind ... I keep thinking about where my tongue would be if I weren't thinking about it, and then I can feel it sort of pressing against my teeth."
Loudly declaring this the dumbest thing she's ever heard, Lucy scowls away. But a few steps down the corridor, she stops dead in her tracks. She clutches her own mouth. Suddenly she's aware of her tongue too. She runs back and chases him round the room, shouting, "You blockhead!" with her gigantic booming gob.
Occasionally, late at night, while trying to sleep and failing, I experience something similar - except instead of being aware of my tongue, I'm aware of my entire body, the entire world, and the whole of reality itself. It's like waking from a dream, or a light going on, or a giant "YOU ARE HERE" sign appearing in the sky. The mere fact that I'm actually real and actually breathing suddenly hits me in the head with a thwack. It leaves me giddy. It causes a brief surge of clammy, bubbling anxiety, like the opening stages of a panic attack. The moment soon passes, but while it lasts it's strangely terrifying.
