I think I replied to your first post about this

Any thing that happens ( i.e the man in the black robe ) that terminates an object or a place can be like a form of closure. If your brain knows the person is dead, you don't have to dream about it anymore.

By the way, my grandfather has terrible nightmares every night. He doesn't want to control, just stop having them.

The other night, he had a dream where some kind of animal cut his arm. It swelled up and popped, and worms started gushing out of it.