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.
I pretty much live in mine now, even when I’m not running or cycling. I just have low level music playing all day, and I can still interact with the world. And for whatever reason, it’s easy to process the music and people talking to me without my brain getting overloaded like it does when I try and do that with regular headphones (even those with sound passthrough)