Emily, I discovered that if I wake from a nightmare and try to sort out what my subconscious is trying to tell me, then my next dreams tend to be more gentle. Sounds crazy, I know, but once it's got my attention, it doesn't have to resort to such heavy-handed messages. Might be worth a try...
Actually, I didn't explain that well. Every dream you have is an attempt by your subconscious to communicate a message to you, and the subject matter on the dream doesn't necessarily have anything to do with the message. And every single character in your dream is an aspect of your personality. So if you have dreams about someone trying to kill you, it's likely that some part of you feels stifled or something like that.