I've read but not tried that if we write down what the dream or nightmare was as soon as we wake up can help. Not sure if I've remembered that correctly but my logic is telling me that maybe by acknowledging the nightmare by writing it down that maybe whatever thought or feeling that is behind that nightmare is somehow acknowledged so it can let you move on. ?? Thoughts anyone?
Maybe not so relevant if the nightmares are a different theme each time. ...but could be linked.

Definitely the fear of having another nightmare can prevent you from falling to sleep, and a sleep full of nightmares (and even dreams) is not a restful sleep. So how you are feeling the next day is understandable as you are losing more and more and more sleep.

Ways to avoid them in the first place? Are you someone who could go for a walk in the evening? Natural feel good endorphins and all that. Exercise to relax the body and mind.

Or if you are someone who could write or type or speak a nightly journal/diary? That may kind of "debrief" your mind so that your mind has less to process as you sleep?

This coming from the woman who has shockingly disturbed sleeps and on waking from yet another intensely action packed dream which often end with a frightening outcome that has me gasping or crying myself into consciousness. ....I don't do any of the things I suggest. I pick up my night time filtered phone and play mindless solitaire until I'm about to drop my phone and fall back asleep. If the nightmare is there on the edge of my mind I play solitaire again. Not exactly great for my sleep but it does keep the nightmare from returning that night.

If too many nights of broken sleep in a row is leaving me feeling unable to cope, that's when I will medicate. My doctor and I have worked our way through an assortment of sleeping aids but I dislike ANY sensation of my mind being foggy or even worse. ....shutting down. I find that sensation terrifying. I have also tried zopiclone which leaves me with a wide awake mind but a heavy body that feels like it has been switched off somehow. ...again, I dislike the sensation but at least that one isn't so scary. But it's not helpful to me as my mind is still frantically ticking over so didn't help for sleep.

Quite by accident we found my go-to drug for sleep. Drowsy anti histamine. I have it prescribed from the doctor for when my cetirazine daytime anti histamine hasn't had enough effect on my skin that flares if I've been in the garden too long. My choice is either a second cetirazine if I feel a more mild anti histamine will suffice. ....or ( looking at the box) promethazine hydrochloride. It's apparently stronger according to the doctor and pharmacist but will make me sleepy. ....and it does but in the most natural. ..getting sleepy. ....way. I know that I will need to take it around 6 as 1) it takes quite a long time with me for it to have enough effect. ...and very importantly 2) if I don't take it early enough I feel a kind of hangover in the morning.
My doctor is delighted as it is non addictive and safe.

I'm delighted as I fall asleep more naturally. ...meaning that I get heavy eyed, I yawn, I can still eat dinner and do my chores with our pets so I'm neglecting anyone. I can mooch through a shower and teeth and anything else that needs doing. I can still read something or watch something with my husband. And when I choose. ..important to me. ...when I CHOOSE to go to bed ....I slip so naturally to sleep without the usual brain chatter etc. ... And because my brain is so much quieter, and my body is so relaxed but not in a drugged "feeling" way. .... my body and mind is ready to fall asleep around the time my husband falls asleep which is around 9.30 ~ 10. So much better than the 1am~3am which is my norm.

The huge plus is that my brain stays peaceful on those nights with this anti histamine in my system. No dreams. No nightmares. Just restful sleep.

I choose NOT to take this drug every night. I don't even take it every week. Maybe I should and my doctor would be OK with that. I choose not to as I do want to learn other ways to sleep healthily. I don't want to be dependent on a medication to sleep.

I hope that you can take something from this.