You've reached exam time and you definitely should have been revising up to this point so you arrive at the inevitable result of having to force yourself into a deep state of learnings. The coma is usually brought on by a deep sense of fear and usually occurs after a fortnight of procrastination.
Man, I didn't revise at all over the last two weeks off, now I've slipped into a revision coma
*On exam day* I only started revising last night, I didn't sleep at all even though I was in a revision coma