When I was having a hard time in therapy most sessions and it would get time for bed on a therapy day I knew I'd have difficult dreams and be afraid to go to sleep but then I realized it's part of the process and the dreams are really just dreams and cannot hurt me. I started trying to pay attention to them and record them and take an interest in them and they became more experiments to me rather than quite so painful.

Can you write out the nightmare and write out other endings or possibilities and see if you can dream them instead? Can you wake yourself at a spot you don't like instead of continuing or do like they did in Harry Potter with the "Riddikulus"/boggart spell thing?