A lot of horror stories, thrillers, or whatever they want to call themselves, are the kind of fun, controlled horror you have at an amusement park. Cabin in the Woods or Scream are great examples of those. They're a thrill ride, and the rider knows it's all in fun.

Then there are the serious horror stories. The tragedies, the hopeless, miserable cases. I'm not as big on these, but they have some interesting qualities, as well.

Even in the most serious, depressing horror story, the audience needs some time to breathe. They'll take any excuse they can get to surface for levity before diving back into horror. If the story keeps the same horrific tone the whole time, readers lose interest, and it loses all but an obsessive cult audience. Not all of them use humor, but they have points where they let the reader breathe. Think of it like a warped sine wave. the horror ramps up, gets really intense for a few pages, then lowers itself into a dimmer sense of normalcy to allow the reader to digest it and give them a chance to feel a bit of dread before plunging them into the horror again.

Well, unless they're short fiction. In short fiction you don't have to pace yourself.