I've had these through out most of my life, the earliest was when I was 9, scared the shit out of me, just when I thought I coul sleep agin after watching Nightmare in Elm street, this shit happens. I was paralyzed. I tried to look around but my eyes were twitching and blinking and heart racing under seize of this half awake/sleep state, then I heard that laughing that actualy still kind of mock me to this day, those laughs were just utterly disgusting in a way that was humiliating, like they were literally lauhing at me and wasn't because of they were hysterical. Scared the fuck out of me I cried when I broke out if it.
That was the first time.
The second time was a lot later like when I was 11 I heard these murmurs and and a wierd raspy exhale every 2 or 3 seconds, then in the distance I heard whimpering, my heart was racing again and when I broke free I almost cried again.
This shit and my dreams feel to real and leave me feeling emotional in a way I can't explain, so with this I was curious. Like Mrjingles said It's a bridge, you're here and not, I may not be a dream master I can control my dreams quite well and with this it's a lot easier, but my mind always throws elements of surprise like not being to spawn light when you need it or a gun. My thoughts are like " nah bro, this scenario is real, no cheating"
It took training breaking free from it if you have weird fucked up rampant thoughts especially when you're plighted by depression and anxiety and such. I foun that focusing ona limb whatever it may be for me was curling my toes. Just concentrate there and eventually you'll fully wake.
This is also good for a sound sleep if you remain calm and keep composure.
This normally it happens as I'm trying to go to sleep. I would dose off slightly and wake a little. So ever my night for awhile I tried to enter this state, I got good at it now.