Nightmares

I don't really know what nightmares are all about. I actually am planning on taking a class next year on what sleep deprivation and dreams/nightmares are all about because I've been ridiculously curious. I had the worst night last night. I tossed and turned for hours and had nightmares for what seemed like hours on hours. I did go to bed really upset last night but what amazes me is that my entire day had been the completely opposite. How is it possible that something so simple and so minute in comparison to the rest of the day could completely take over the mind and as a result, the night? I actually can't wait to explore dreams in a class next year because it is actually mind blowing to me that your own mind can completely turn against you like that.