Glad to hear you're on the mend, Barry.
I think a lot of us never realize something abnormal is going on until the last minute.
Seventeen years ago, right after retirement, we visited my older son in CO. My son and I spent 3-4 hours hiking vigorously at 9000 feet and all was good. A few weeks later I was walking leisurely around our lake back in MI and found myself out of breath every 50 steps or so. I've never been much of a runner, but I could walk all day. Went to the doctor and he said he thought I had nasal congestion, but sent me to a cardiologist "just in case". That was on a Friday and the cardiologist said he would see me Tuesday morning in surgery. 90% blockage of one of the coronary arteries. Stent installed and been fine ever since. I never had a clue.