Pass the tissues

Why is it one minute you go to bed feeling fine, then you wake up next morning, coughing and with a stuffy head and are running round looking for the tissue box. This happened to me yesterday and no doubt will h appen again over winter. The common cold reduced me to being in bed early last night with a shopping bag full of used tissues next to the bed and a very sore red nose. Sleep was not great, you wake at 2am when the cold tablets have worn off and then spend the rest of the night only getting short naps. Well i am going to realy look great tonight when I go out on the town. grrr