Agoraphobia & Social Anxiety Support Group
Agoraphobia is an anxiety disorder, often precipitated by the fear of having a panic attack in a setting from which there is no easy means of escape. As a result, sufferers of agoraphobia may avoid public and/or unfamiliar places. In severe cases, the sufferer may become confined to their home, experiencing difficulty traveling from this "safe place."
Don't really know how to express this, but :
You don't necesserarily have to control this as nightmares have that power of scaring the hell out of us, it's a normal reaction to the deep emotions they make us feel. And coupled with anxiety, the reaction you experince reaction is not that surprising.
I'm certainly no psychologist, but you could try doing activities that get your focus (not too intense though) before sleeping, bonus if it can make you calmer as well.