I bought a piece of 1.5 inch stiff foam to try to fix a sag in a bed. It didn’t work but having that thick piece of solid foam around has been a life saver.
Need something flat to put a laptop on? Throw it on the foam. Going to be doing something that requires you to be on your knees for a while? Get the foam!
It went from stupid purchase to something I’d gladly replace if it broke.
You can buy a DIY kit for ~$20. Mine work great, though I’ve never gotten professional ones so I can’t compare.
Radian on Amazon, they work like two-part epoxy. You can also make custom fit earbud covers to have noise cancelling earbuds that are super comfortable. If you get the Radian kit, put a water bottle cap sized spacer between your teeth while they cure. They will seal better.
https://www.radians.com/products/composite-radians-custom-molded-earplugs-and-accessories?hsLang=en#features