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
It’s for the first half. There’s no objective evidence this approach works. The OP may also recover from colds quickly without the vitamin / protein intervention, may judge symptoms differently, or may not accurately track results (e.g. dismiss cases where the opposite was true).