Mystery of Mysteries

This is a tale of a man plagued by nightmares brought by guilt.
Nightmares are different than bad dreams. Both can be very disturbing, but only a nightmare can wake you up.
The word nightmare is derived from an old English term "mare," which is a mythical demon who visits those who sleep alone and torment them with frightening dreams while they sleep.
When you wake, the nightmare is over. Or is it?