...breathing. The most natural thing to do. Your body doesn't ask you if you want to breathe. Until of course, it tells you to do something about your breathing when you have a cold and the nose houses stuff it shouldn't.
S for strength. The most natural thing for the body. Until of course we put the bed in the room where we spend a hell lot of time and where this bed constantly blocks a range of movements that our body is naturally made for.
We can't survive without breathing. We can survive a long time without strength. Can we survive a long time enjoyably without strength?