Imagine if that rest will do nothing for that headache and its there morning day and night. Or some injury-related pain which simply can't be downtuned. Plus when old, half of the body aches, all old injuries and general deterioration.

I had only very brief experiences with longer intense pain but it made my mind into pudding and desperate knot of how-to-stop-this-at-all-costs. Normal life is not possible and sanity is not granted.