It begins in the middle, the way that most things do, as a spark, a ragged breath in the soft darkness where we go to dream, the secret place inside where tiny fragile things are born. It begins as a thought, no more than a shy flicker of maybe, and the sweet vanilla scent of chance.
In 24hours it will have crept into your being, established now, snuggly-deep in flesh and mind, and running toxic madness through your veins. Initial symptoms are mild and are often confused with those of lesser afflictions. Nothing will matter, though everything will remind you, lest you should forget. The ability to remember everyday things will desert you. You will experience some sleep loss.
Finally, it will become itself. At its most severe, it will present in shards of light, in fire, and heat, and waves of impulse never imagined. Concentration will be greatly impaired. Sufferers have reported episodes of dizziness which hinder any effort to engage with reality.
Extraordinary results are guaranteed. Enjoy the trip!