Of course we all have sleep atonia every night, but are just unaware of it. I have only once experienced sleep paralysis, which is where you become aware of your atonia, but it was strangely comforting, because I knew it was related to the lucid dream I had just experienced. For me it lasted just a few seconds and then wore off. It was weird, because at first I thought, "I can just move anytime I want to", but I didn't want to because I was thinking about trying to reenter the dream, but I realised I was too awake, and then it dawned on me that I really couldn't move. Because I knew what it was, it didn't worry me at all.
You're not crazy being afraid of the unknown, but think of it a bit like a rollercoaster ride. It might be a bit scary, but it's a fun ride! (apologies if you hate rollercoasters!)