Different types of dreams can behave like a volume setting in helping you to release or let go of unproductive thoughts. The more dramatic the dream, the more likely you will remember it and explore its meaning. Nightmares are just a sign that something significant that has been repressed will serve you better if you can examine and come to terms with it. When killing is the theme of a dream, you may need to address self defeating behavior and ‘put it to rest.’ See Murder, Attack and Being Chased and Corpse.