I have had sleep paralysis for years now and while at first it is scary you do get used to it and learn to relax. somewhere on this site it mentions concentrate on your breathing and try and concentrate on moving one part of your body, just like uma thurman with her big toe in kill bill hehe. Those who mention breathing problems in these posts this is also normal as your breathing naturally slows down when in a sleep state, this can make your chest feel tight or as though someone is sat on top of you. the first time i experianced SP i was convinced it was a ghost pinning me down. It is scary stuff at first but once you know the cause its much more easier to cope with and i actually find it quite intresting when they now occur