Well, I am a little afraid as I am near some things that may get me control over LDing, but now I’m a little scared. Today we were reading children of the corn in English and the end of the story nearly made me vomit(I was nauseaus already, but that made things a lot worse). Now I’m afraid that if I do things wrong, I’ll end up in a nightmare and picture what I invisioned in hte story today, but more realistic. Is this practical? Can I avoid it without mental scarring?
Whatever you do, I wouldn’t think about evil clowns or zombies or scary crap like that because I fear that one could lose control of the dream and that sinister (but lovable) subconscious of yours could take the nightmare to the extreme
(although it would help me find inspiration for my novels)
Your fear is irrational.
Mental scarring? Relax bud, you’ll be fine. I’d be more worried about vomiting in class in regards to mental scarring… 
But yes, lucid dreams are fine. I haven’t had a lucid nightmare yet, and I’ve been doing this for something like 9 months. So yeah, don’t worry about it.
If you do have a nightmare, just remember it is just a dream, and regardless what happens, it won’t hurt you.