Feeling a little undead?

The worst feeling in the world, aside from having your heart shattered into a googleplex of pieces, metaphorically speaking, is the feeling one gets when medicine, particularly cold medicine, is leaving the system. I hate this fuzzy, cottonmouth, out-of-body, semiconscious feeling (I try to use as many apt adjectives as possible, but no combination gives it full justice) that has been constantly a part of my waking moments for the past week. It's as if I am missing out on living to the full extent that I can, that I am normally able to on a regular basis. Yet, people chase this feeling, filling their systems with foreign elements that ultimately only do harm to one's system. One question lingers in the hollows of my drug-addled mind: Why?