One month ago today, I had a persistent cough and I couldn't catch my breath when I exerted myself. I'd been told early in the summer that I had allergic bronchitis, and so I believed that the cough and the shortness of breath were complications of that. So I wasn't worried about it.
Three days later I was in the emergency room, in deep hypertensive emergency, with stage 1 heart and kidney failure. The cough and shortness of breath weren't allergic; it was because my blood pressure was so high (nearly twice the upper bound of normal levels), and my heart's capacity to pump blood was so low (about a third of what a healthy heart could produce), that I had fluid building up in my lungs. I'd gone to the doctor because I had started noticing very mild chest pain and swelling in my feet; the doctor took one look at my blood pressure and said, "We're not legally allowed to treat you here. You need to go to the hospital."
So I ended up staying in the hospital for three days (one in the intensive care unit, two in a constant-monitoring unit). It was a miracle, I was told, that I hadn't had a stroke. Their best guess, as far as I understand it, is that it had started not with allergies but with a virus, which had made its way into my heart; the infection had caused the heart dysfunction, which had spiked my blood pressure, which had caused the kidney dysfunction.
I've been out of the hospital for three weeks now. I'm on vast quantities of medication - to keep my blood pressure low, to get my kidneys going again, and to deal with anemia and a Vitamin D deficiency that were apparently also complications of the heart failure. I still can't exert myself much; I don't really notice any problems anymore doing everyday things (I was having trouble walking around a grocery store or climbing stairs without getting winded, before the hospital) but walking a mile takes a lot out of me, and I can't even think about running. I strictly limit my sodium intake (and man, it's not until you start monitoring sodium that you realize just how much of the stuff is in everyday foods), and I drink lots of water (at least a gallon a day, in addition to what I get from other foods and drinks). I have a home blood pressure kit, and take my blood pressure and pulse once a day, like clockwork.
And a month ago, I believed that I just had bad allergies.
Maybe it's time to check some other beliefs, too, just to make sure they're not hiding danger - or hiding damage already inflicted.