What has to happen in a story to scare you?

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Last night, before bed, I was reading some supposedly terrifying stories off of facebook. It was actually a third party site that I was directed to after perusing a facebook page, but I digress. The stories within the site were okay, but not at all frightening to me. There was one, somewhat frightening but that I have heard several times before. The familiarity of the story did not make it less frightening, but the beginning sentences were so familiar that I did decide to forgo reading it last night. I've read stories from creepypasta and nosleep (reddit sub) that have been frightening. I have watch television shows or movies that have their jump scares. Even those stories that elude to something but don't quite follow through can be frightening. However, none of the books I've read lately have been all that terrifying. I suppose the familiarity of concepts have helped me from getting frightened. That is to say, that while the books were enjoyable, the plots were so alike / familiar that the stories weren't terrifying to me. To answer my own question, what has to happen in a story to scare me? The ending of the story has to be left to the reader's imagination. No suggestion by the author should be hinted at at all. If I feel as if the author has suggested / hinted at a conclusion, or a possible conclusion? The thrill or fear is gone for me. I've already allowed my mind to conjure up possibilities by that point and the fear factor is ruined for me. An ending has to be so abrupt, and so unknown that it only allows my mind to wander AFTER I've finished the book and not before. I hope this makes sense to everyone. Let's see, anything with an entity going after children is frightening to me, even today. Those urban legends of the babysitter getting a call on the phone and getting the police to trace it only to find out it was coming from upstairs? That creeps me out... A long, drawn out scene can be frightening with the right mood. What has to happen in a story to frighten you? Or do you read / watch frightening things at all?