By the time I was 8 or 9 I believed that devils, Satan, Hell, ghosts, and other such things were as real as my bicycle. I "knew" they were true because of my church, my family, and cultural influence. These things scared me and gave me nightmares. One particularly terrible nightmare I still remember is when ghosts came out of my huge toy chest, and dragged me out of my bed and into my toy chest and straight down to Hell.
Very very scary.
My mother gave me some advice, she told me that I could control my dreams if I really wanted to. We had an old, black and white Zenith TV with a big, clunky channel knob. Mom told me to visualize this channel knob during a nightmare, and then just reach out and 'change the channel' if the nightmare was too bad.
It worked very well, and for the rest of my life I've been able to recognize a nightmare while it was happening and 'do' something about it.
As a side effect of being an Atheist and a Skeptic I've found that after I truly lost my belief in the supernatural, it stopped appearing in my dreams. The few times themes of Hell or evil spirits appeared I immediately found them to be ridiculous.
In fact, the very ridiculousness of some nightmares is so funny to me that now I look forward to those sorts of dreams. Being chased by monsters is fun if you don't believe it for a moment. On several occasions I've awoken myself by actually laughing at a ridiculous situation in a dream.
I still get an occasional nightmare that actually frightens me, but they are very rare. I just woke up from one.
By now most of the world has seen or heard of the movie Terminator, where a California governor stars as a machine in a world where machines are bent on creating a machine uprising against humans.
Actually the concept is valid. The mathematician John Von Neumann proposed that machines could be designed to build copies of themselves out of available materials. Very small machines would be able to manipulate materials on a more basic level and so would have even more materials available to make copies of themselves.
The science fiction book "Einstein's Bridge" by University of Washington physics professor John Cramer takes the concept of Von Neumann machines to its limit, and overcomes a lot of Hollywood bad physics. The machines in this book only make a brief appearance fighting against humans, where they overtake everyone in the world in mere hours. (Yes, the world ends halfway through the book - sorry for the spoiler.)
My dream included electronics, robotics, Von Neumann machines out of (human) control. The machines were not 'evil' - they just seemed so because they competed voraciously for the same resources as humans.
It was a frightening dream for me, because I know too much about what is plausible in technology to NOT think about it while in a dreaming state. I couldn't 'change the channel' because I was too fascinated with the implications and possible scenarios. But it definitely wasn't helping my rest! So I forced myself awake.
And of course there is one tried and true method for 'exorcising' the evil creatures of bad dreams. It's a method that humankind has been using for all of our history. We purge our nightmares by turning them into stories. By talking about them.
And now I find the nightmare has turned ridiculous, and I'm sleepy once again.
I'm going back to bed. Goodnight all.