My father had been feeling short of breath for about a week. Thinking he must have bronchitis or pneumonia, we took him to the hospital to be checked out. They took him in immediately upon hearing he was short of breath. After doing tests, they discovered he had a heart attack.
That night when I went to bed, it took me a while to get to sleep. I kept thinking and worrying. Worse, I would start to doze off, then suddenly feel like I couldn't breathe, causing me to wake and take a gasp of air. It was likely just nerves messing with my mind. Despite telling myself this, I repeated it a few times more before finally getting to sleep.
The following day, I heard that Dad didn't have a very good night. At one point during the night, he suddenly felt like he couldn't breathe, and the doctors had to put him on oxygen. He told us that he had panicked when he found he was unable to breathe. My mother, who had asthma attacks as a child, said that she understood how he felt.
It all makes you realize just how precious air is.