Create a compressed archive of them - use a relatively slow algorithm or have high compression settings. Burn this to a DVD (or some other external media with a slow transfer rate) - delete your local copies. Then to play them again you'll need to copy them back, extract the archive etc. When you want to deny yourself access again just ...
I have this same issue too, and I'm improving. Aiming for better sleep in mummy sleeping bags. I go for a comfy pillow under my head. I count my breaths, aiming for a large number, usually 200. I start nodding off after a while. Have managed a fair bit of sleep like this. This is a WIP, not totally solved yet. Happy to hear other people's thoughts.
You could use the postal service.
Copy the desired files onto removable media. (Delete the original.)
Mail the copy to yourself. (Use appropriate class for delay - Parcel Post is slower than First Class, for example.
Await the delivery of the copy.
Here in Canada, we laughingly refer to high postal rates as acceptable because half of the expense includes "...
Don't use time (elapsed or absolute) for irregularly-spaced events at different locations.
Use GPS (position determined by Global Positioning Satellite) data to determine. your destination.
Recently, my buddy lent me his extra cellphone with an application that has a map function that works by GPS. He downloaded the relevant maps for me. I activated the ...
Since you are able to fall asleep while on the side, I will not go into the generics.
Analyze your mind state between the two positions:
on the side;
on the back.
Also, if relevant, understand the differences in what you feel in your body, thoughts... Anything.
Once you become aware of differences, try to mimic the "on the side" things while on the back.