Our bodies are made so that most of the time we aren't even aware of all the basic functions they perform. We take them for granted (which, essentially, they are) until one (or more) of those functions start giving us trouble.
We can live without food for many days, without water for a few days (not that I want to try), but try living more than a few minutes without breathing. Good thing we do it automatically, yes?
And then all of the sudden this automatic usually effortless activity becomes difficult. You feel exhausted and slightly feverish and you want to get some sleep. But, whichever way you turn, something is blocking your respiratory channels. Where does all that mucus come from? You turn around in bed trying to find a reasonably comfortable position, but in vain. Oh well... here goes a good night's sleep. And you feel more tired in the morning than you did last night. And you still can't breathe. And there are piles of used Kleenex all over the place. And you drink gallons of tea and overdose yourself with vitamin C and paracetamol and whatever you can think of and wonder whether you'll ever recover from this ordeal.
Damn that cold!