This happened to me a couple weeks ago. I was not feeling well Thurs and Fri, woke up Sat morning feeling about the same, a mild cold, maybe even slightly feverish. Figured I'd go for my club ride and bail out if I didn't improve. Ended up riding 55 miles that day and felt better and better through the morning, got home and felt great and the cold did not come back. Maybe it had run its course anyway and riding had nothing to do with it, don't really know, but was pleased with the outcome.