Lie down on a grassy slope and roll down the hill, over and over, until when you stand up, the whole landscape is spinning around you. Imagine what it would feel like if that spinning sensation lasted for hours.
Take that split second of movement on a very fast amusement park ride when your body goes one way and your head goes the other, your skull knocking against reality - and stretch it out to last four or five hours.
Imagine a world in which every sound, every vibration has been amplified so that your entire self is overwhelmed with noise, confused by a kaleidoscope of sound and you cannot stand the high-pitched sound of your own child's voice.
Imagine a piercing light shining into your eyes, stinging, probing, cruel until you beg fate to put you in a dark room where you can close them. But when you close them, you keep seeing patterns, red on black, strange twisting patterns that rub against the inside of your brain.
An alien slug crawls into your ear and oozes its grey self across the inside of your head, turning and twisting all the pieces until you have to vomit.
And it's actually a relief to vomit because that feels better than anything else.