I guess colds and flus don't hit me too hard as I have only taken one legit sick day off work in the last 5-6 years. **knocks on wood**
However right around end of January and all of February I tend to be my stuffy. This is my biggest issue when I try to run; breathing in enough air. Usually I try to take easy runs but I spend the first mile or so working on a breathing pattern!
But yes many people I know feel "weighted" down during flu spells and it hinders them whether it be running, skiing, lifting, etc. Like you, those are the people that push it when hard times come while most would just roll over and sleep on it. Great job working through it! Just don't over do it! 