Not sure if this is helpful or relevant to this situation since we're dealing with injuries, but it's something comforting I think of when I can't sleep (apart from Bing Crosby singing me lullabies )

There was a study that I remember reading in linguistics at college that talked about cross-cultural sleep patterns and how the solid 8 hours we venerate in the West is both a new and potentially unrealistic ideal for some people. There have been a few more recent studies, too.

Apparently, they studied hunter-gatherer groups to try and get a sense for how our ancestors might have slept, and noticed that folks slept about 4 hours at a time with a little break of wakefulness in between-- something called bi-modal sleep. The theory is that it meant one person or another in the group was awake at all times during the night and could keep an eye or ear out.

What they say is that sometimes when people wake up in the middle of the night, they keep themselves up by worrying about how they're not getting a good night's sleep. If instead they say to themselves, this is normal and human and the way we've slept for thousands and thousands of years and I am simply in touch with that, and spend a little time doing something relaxing, they can still get a good night's sleep even with a break in between cycles.

It's just something my little nerdy self finds cozy and comforting-- when I wake up in the middle of the night, instead of thinking i'm doing it wrong, i can think about my ancestors sleeping under the stars and connect with that idea