For me, nightmare is just as beautiful as my other sweet dreams.
I haven’t had any kind of nightmare these days (sigh), the most memorable and frightening nightmare I had would be when all of my friends and family members suddenly turned in to vampires, one by one, each of them try to bite new victim in a planned strategical pattern, I and my cousin (weird, why him!?) struggle to survive, to avoid being bitten, and to hide whenever we can from people we suspect as vampires. In the end, It’s just me, alone, and I finally accept the fate I must face, I let myself fall in to their desire, someone bit me, I become a vampire, and the next feeling I got is trying to bite other unaffected victims.
I love it when I experienced adrenaline-pumping situation in my nightmare (i.e. I don’t have to fall off a cliff to get that adrenaline while I could experience it in my nightmare). Nightmare is beneficial, yet rare.