[Immarsecice]

I think this could be related to the "tetris effect." It's a bit as if our brain had "cache," like on a CPU, a zone where the most recent memories are stored for quicker access later on. This is a mental device we have to help us with repetitive actions. For instance, if you're playing tennis, you might want to warm up by playing a couple of practice balls so that your tennis-playing reflexes are fresh in your mind. After a few balls, the motions will be in your "cache" and you'll be ready to use them quicker and more appropriately than if you had not practiced beforehand.

This cache applies to everything we do, and hypnogogics seem to be very influenced by it. If you play tetris for 3 hours and then go to sleep, you'll start seeing falling blocks, playing tetris in your head. If you've been browsing the internet and typing for 3 hours, you'll see scrollbars and frames and text boxes... If you've been watching a movie, you might see things that happened in the movie.

Mantras, affirmations, relaxation and visualization exercises before sleep all influence the cache, which ultimately dictates what will happen in the trance state.

Now it's just a matter of using this to your advantage