I've had one experience in my life that might be interpreted as "mystical" – actually a series of basically the same experience. The first time it happened was when I was 14 or 15, and the last time it happened was just a few months ago (it has become such that it isn't even worth mentioning when it happens). After all this time, I still don't know what to make of it.
A full description of the evolution of the experience would bore anyone to tears, but there are commonalities which make it obvious that it's the same thing. It always happens when I'm drifting off to sleep, and suddenly I'd be fully conscious but completely paralyzed, unable to move, speak, shout, or scream, unable to mentally "snap out of it".
The experience has evolved through the years. Needless to say, the first time was really scary, and involved blinding light, deafening noise, and pure, unadulterated panic. The panic abated over subsequent occurences when I became pretty confident that I would always come out of it. Eventually, even the "paralysis" changed from literal immobility to more of a sense; like it was a space or a different form of consciousness.
Now when it happens, like it did most recently, I can sense it coming on before it actually hits; like hearing a train getting louder through a long tunnel. I can avoid it by forcing myself awake, but I usually let it happen because it's still interesting. I just let it happen and I "explore" the experience/space, but nothing "mystical" ever comes out of it. No new knowledge or revelation. It just ends and I go to sleep and wake up the next morning none the different.
Actually, there is an excellent description of the exact experience in a book called "The Woman Warrior: A Memoir of a Girlhood Among Ghosts" by Maxine Hong Kingston, only she describes the experience as being attacked by a ghost. I almost plotzed when I read that passage in the book. It's a great book anyway, go read it.
But I guess that's the whole point of this. I had this arbitrary, subjective experience which I can't recreate on demand or explain rationally, but which also can be interpreted any number of ways, depending on context. Having been raised in this modern, scientific, technological age, my impulse is to not interpret it mystically, but "rationally". Since I can't find any rational explanation, it has become an empty experience, one not even worth mentioning when it happens.
In another context, I might believe that I was being attacked by a ghost. In another context, I might believe that I was experiencing something divine or other-worldly and search for a message in the experience. I don't discount the possibilities, it's just that I was raised and educated in this particular context, and maybe I'm missing something because of it.
(sleep paralysis tag added retroactively -ed.)