I've had a long history of respiratory infections. I can remember my first case of pneumonia during my first year of graduate school. My digestive system rebelled against the antibiotic erythromycin and I was growing weaker and weaker until a nurse suggested yogurt and all was well again.
I had recurring pneumonia for a decade or so every year or two. I imagine with each case my system became more susceptible. Finally a kindly nurse pointed out that I had a standard trajectory: sinus infection to sore throat to pneumonia, and that if I was faithful with irrigating my sinuses I could stop the progression early on.
That has worked for me, unpleasant as it is to irrigate daily. I still get colds, sore throats, etc. but since then no pneumonia for which I am exceedingly grateful.
This came to mind as I am now recovering from a chest cold and sore throat. April seems to be when I am most worn-down physically and prone to catching something. I am glad to be on the other side of it now.