Place a glass of water out at your bedside before you go to sleep. In the morning empty
it into the toilet, using the anti-dexter hand. Rinse the glass out three times.
Do this every night, not just when you are having nightmares.
Burning Benzoin incense in the room will raise the vibration of the room, and keep
most negative spirit influences away.
If you were born with the Sun in Gemini, you are susceptible to this kind of influence
every lunar month. (Statistically, you are more susceptible than the average person.)
You should note what sign the moon is in when you have these nightmares,
and be certain to clean your room physically the day before the moon enters that sign.
This, using the night water, and burning incense will be of some assistance to you.