Is It a Disorder If...... you don't allow it to take over your life? I'll self diagnose myself with nightmare disorder. I have nightmares nearly every sleep cycle or nap I take. They vary in theme but usually follow the path of current or past life events. I remember them vividly, but I don't collect or hang onto them unless I feel they have some kind of important message... like "Be kinder to yourself, and take it easy!"
I've learned to accept that I will most likely never have sleep without anxiety. These days I have trained myself to wake up if the dream is overly unpleasant and coax myself back to sleep with the intention of affecting the dream (if it returns) towards the positive.
There was a time where I felt captive to a naughty and cruel brain. Those were miserable days (or rather, nights). Of course, I still have disturbing nightmares, but I have learned to snap out of or calm anxiety and embrace the joy I experience in my waking hours over the fear I feel while asleep.