I used to wake up (happened more frequently half a decade ago than it does now) in full SP and I never understood it. Problem was I couldn't breath (have OSA) and I'd panic, and it would be minutes before I could regain full control. Terrible feeling. So I kind of know what you mean, being fully awake and aware but not being able to come out of SP. At least you seem to be comfortable with it and understand what SP is so that's good. Sorry I don't know how you can stop. In SP you can't even control enough bodily functions to scream for help.