How can a simple cold WIPE YOU OUT?

Last week I felt it coming on...15 sneezes in a row, post nasal drip, that chesty feeling.  START AIRBORNE, VITAMIN C, and ECHINICHEA, NOW!!.  After limping through the Philharmonic Friday night, I was DONE.  Sucking throat lozenges, using 4 nebulizer treatments (breathing machine) daily, running, raw nose from constant blowing, gulping meds to lower my fever every 4 hours, and using enough tissue to stock Costco, I still felt LOUSY.  Even my eyes, red rimmed and runny, gave way to the disease, making it impossible to read.  The final blow...Prednisone...a cortisone derivative...the only thing that keeps me from bronchial pneumonia and the hospital!  Never patient with illness, I am dead meat, short tempered, and  yet itchy with "cabin fever".  This morning, after a renewing shower and hair wash...bed head does not do my hair justice...I cooked breakfast for Eddie and collapsed in a heap...back to dead meat.  How is it that a simple cold can wipe you out?