I've been digging into Quantum Mechanics the last couple of months and really dove into the conscious part of this science.
Imagine yourself at a deserted cemetery 200 miles from the nearest city. No lights, midnight, no sound, just the sound of your foot stepping on the sand and dry leaves as you walk between the graves.
Now the last thing you think of at this moment is picking the Laundry or preparing for work tomorrow, or the virus at your machine or the chapter you skipped from the last book you read. You will keep thinking that some ghost will come and squeeze your soul out of the tip of your toe while screaming very load. Or perhaps an ugly old grandy coming out of one of the graves and running very fast with her back bend towards you to eat your pretty head.
Those thoughts become so sharp, so clear, so thin that increases what physicists called the Energy Density and make those thoughts move to a part of your brain called the Frontal Lobe. At this time, those thoughts, those ideas, those concepts become real.
So you might really see something really weird coming to you because you believed that it will come to you.
Should you achieve this in a fear mode, you can do the same in the normal mode. Say like, you can create a 20 BD in your hand if you believed in it enough. That's how prayers work too to a certain extent. Its about what you believe in.
EDIT: That is turned into a movie. The Apparition