Napping during the day seems to be a very common practice. It leaves me exhausted but less attacked by nightmares and night terrors. Both are hard to tolerate, for me.
For me they're very different, my nightmares are abuse-related and cruel, twisted, with a clear narrative, they can be very cruel or just stupid and meaningless, but they have a story to them. The night terrors seem to be early in the morning with no storyline, very vivid and crazy, with nothing to with anything at all, they're just moments of pure horror beyond description. Like my brain is locked into extreme fight/flight and is trying to escape but can't. Urgh.
Medical marijuana helped me weaken both a bit but they keep coming.
I used to be mad at myself for going to bed so late ever since I was a kid. Fought and fought with myself, till I read about PTSD and how daytime napping seems to lessen the pain and realized I'd been doing the same for as long as I can remember.
Nowadays what I do is I literally just give up. I read books all night long instead of trying to rest. If I can manage it I make use of time. I just ignore the fact that it's dark, makes no difference, I do what my body demands. And if I surprisingly doze off at some point once in a while, well fine, mistakes happen. Not pushing it and not trying to force myself to relax into sleep (an oxymoron anyway) seems to make it a little easier. Maybe.
But I guess it's hard to sustain long term. My body goes through "waves" of sleeplessness: I don't sleep at all for a week or so, then I'm so tired and out of it I get one night's sleep (I guess it's either that or brain damage) or two at the most, then no sleep again. In general, I think I never slept well in my life.
On the rare occasions I've been able to meditate and relax my body before I went to sleep, it had a really positive effect. But it's not easy... nighttime is when I usually feel the worst, fewer distractions, so sitting quietly with myself at night can be rough. Still, when I managed it it's been worth it. Getting myself properly tired, too. Physical exercise (back in the day) helped as well. But (for me) nothing makes the sleep craziness go away completely.