No cure so you gotta rest. Nose is stuffed so you gotta mouth breathe. Throat is dry from mouth breathing. Dry throat makes it painful to swallow. Pain keeps you from sleeping and recovering. Lack of sleep leads to worse symptoms like piercing headaches. Need to rest to get rid of the headaches. Headache and swallowing is too painful to rest properly. Lack of rest perpetuates headaches, nose congestion, dry throat, painful swallowing.
What is this BS
Some of those symptoms are caused by the virus as part of its strategy for spreading. They make you likely to leak infectious fluid from your nose and mouth. Meanwhile your body has to learn how to recognize a virus that has evolved to be hard to recognize (and do that without also accidentally “recognizing” some of your own cells and killing you) and then track down every last virus. And there can be billions of viruses, many of which are hiding inside your own cells.
You’d spoil about as fast as food left out of the fridge (but due to bacteria and fungi, not viruses) if not for the constant battle your immune system fights.