Waking reality is not the bottom layer of existence. It is contrived, sewn together by the thin thread of deceit to protect its inhabitants from falling into the void beneath.
Calculators cannot be perfectly exact. Inevitably, any sufficiently complex calculation performed by a calculator will be slightly off, no matter what the calculator is. The margin of this incorrectness can be used to describe an aspect of the calculator's quality.
Now consider the universe. The universe is like an infinitely good calculator. Mathematically speaking, all of the actions of the universe mirror all of the actions of the universe. And naturally so. Any alternative would be logically impossible.
What, then, is the degree of complexity of a mathematical problem that is so large that the logically impossible is called into existence? The only number that can be plugged into a tautology to make it false is infinity. Therefore, for the universe not to be exactly the same as itself, for a defiance of the laws of nature to occur, nature would have to be forced to attempt an operation of infinite complexity. The threads of waking reality extend infinitely far, so to remove them, one must pull with infinite strength.
There is one being who has accomplished this feat. This being is called Pestilence.
Pestilence is the event horizon of the universe incarnate. The creature occupies the void of dreams, and feasts on the fears of sleeping children. It feasts on the fears of sleeping adults, as well. But fears are loose, fleeting. They seep out between the threads and escape too easily on their own for it to be worth dragging them down. No, the food that Pestilence prefers is health.
Pestilence is a tricky fellow. It seeks out prey through lies that instill false hope. "What is your command?" it asks. "X-ray vision? Very well. Then I shall make ye blind." And it laughs and watches its victim's eyes melt, watches its victim cry blood until the arrival of a beautiful sunset that he can no longer see. "What do you wish, little girl?" it may ask the boy's younger sister. "A puppy? Sit still; this will take but a moment." And in the morning, the little girl will shake convulsively in bed, foaming at the mouth and whimpering like a dog. If you ask it for shinier teeth, it will pull them all out.
It shall find the seeker of wealth and make him too ill to work. It shall find the seeker of wisdom and knowledge and instead impart mad cow disease. It drags the human essence into the darkness of sleep, where it will never be seen again but as a reflection of what once was.
But Pestilence, as tricky as it is, does not know all. In life, in physical health, it believes it has found the perfect sustenance, one that will struggle to hold tightly to the threads of reality for as long as Pestilence should please. But there are some biological functions lodged deeply within us, things that should never grow ill or sustain injury. There are certain parts of us that have guided our very construction as organisms, so that we should die before they ever come to harm. The seat of truth itself is upon our shoulders, and when our shoulders are shattered, truth will cease to operate. Should one be greedy enough to allow this to happen, there is a way to circumvent Pestilence's efforts.
It is inevitable that one day, Pestilence will pay you a visit. You may recognize it as a benevolent face with wrinkles and gray hair. Recently, however, it has been manifesting in the forms of its past victims; that way, any future victims who knew previous victims will not be alarmed by the beast's appearance. Pestilence will be wearing a white cloak precisely six feet in length. It will attempt to claim some innocent purpose for this cloak. Do not be fooled, and under no circumstances should you attempt to remove the cloak or request that Pestilence do so itself. Do not inform Pestilence that you recognize it.
Once you have identified the creature, the next step is to fool it. It is not tricky by choice, though it certainly enjoys it nonetheless; once it has harvested a meal, it is bound, by a force other than its own will, to consume it, lest it tear the fabric of reality from underneath it and dissolve to dust. The trick is to compel it to harvest the right meal.
Pestilence will behave as you would expect it to behave if you did not recognize it. It will converse with you and attempt to drive the conversation to a point at which you will naturally be prompted to tell it your innermost desires. Show no fear, no stress; you must not reveal your true understanding of the situation by any means. When the conversation is carried to a point at which you are prompted to speak of your desires, express interest in something related to dreams; say "You know, I've always wanted to be a lucid dreamer" or "I always have nightmares; it would be nice to get a break from them" or something along those lines.
Once you are able to express these desires, you will have won. Before fading away to find its next victim, Pestilence will reluctantly impart unto you an obscure bacterial brain disease. This disease is similar to many brain diseases in that it is degenerative, but it is different in that it only affects the pineal gland.
The pineal gland, known in some religions and alternative medicinal systems as the "third eye" and described by some early neurologists as the "seat of the soul," is a gland in the very middle of one's brain whose secretions regulate sleep and dreams. A damaged pineal gland could mean nightmares or unusual dreams.
A badly damaged pineal gland could entirely eradicate the subject's ability to sleep, dream, pass out, or otherwise dwell in unconsciousness. By forcing Pestilence to sever the sole connection you possess to the surreal world and letting it descend into the surreal world to which it leads, you will have permanently escaped the monster's grip; you will be in perfect health for the rest of your life, save for the inability to go to sleep.
There is only one catch: if you followed the above instructions, henceforth, whenever you close your eyes, you will see fleeting visions flash behind your eyelids of things that do not appear possible. Never speak of these visions.