regulate the temperature of your head so that it's not too hot and not too cold. be prepared to alter the adjustments during your ride. seems like common sense but it can be tricky. for example a cheap clear motel style shower cap over your helmet can cut down the wind and keep your head warm until you heat up, then whip it off and stuff in a pocket. various under helment skul caps and or head sweats can also be used depending on temps.

for me if I take a decongestant I have to take one that doesn't raise blood pressure because I have sensitive blood vessels in my nose that can bleed if I ride hard while on the drug. so I take the over-the-counter drug for ppl w hi blood pressure. it has a "BP" on it. at CVS they have little cards on the shelf and you have to show ID to buy it (I guess to avoid underage kids from abusing it?)

boost your metabolism (which biking is great for)

boost your immune system with supplements and foods - google search for lists

you can do things to your water in the your water bottle too, like add salt, heat before riding, substitute other feel-good fluids, etc

continue to care for yourself once you are at work/school