Sweetdreams?

What is the purpose of dreams? I don't understand why your mind puts these images in your brain, disturbing your sleep. No one can sleep peacefully if there's a huge dinosaur looking monster heading towards your child after they've already eaten your parents. Sometimes you can't even sleep with dreams of your lover being played over and over in your mind. Don't you think it's even just a little annoying trying to get them out of your head during the day and having no control of dreaming about them in the night? Isn't it disturbing having dreams of people you've NEVER seen in your life? Or dreaming of terrible things happening to the most important people to you? Or maybe even dreaming of everything being sooo perfect? Doesn't that annoy anyone? Or is it just me? Having everything be so perfect when you sleep, but then when you wake up, you know it is nothing like what you've dreamt? Having nightmares that scare the hell out of you, and then when you wake up you're terrified to do things with the play-by-play of your dream dictating every move you make? What is the main purpose of dreams? Why can't your mind rest like the rest of your body? Why doesn't your mind sleep? Where does your mind get all of these random scenarios? Just a thought...