You wonder where the idea of human "invincibility" ever came from. I mean, we are born as these helpless little infants, totally dependent on others for care and feeding. And then we live these lives of misadventure where death and defeat loom around every corner.
We are oh so vincible...
Maybe it's just a silly fantasy. A wish, a hope. But it does seem like we all go thru periods of our lives where we really think we can't be destroyed.
Maybe chalk it up to a kind of willful stupidity. Or a flood of teenage hormones. Or useful forgetfulness. Maybe it's in our nature to forget how vulnerable we all are. Otherwise we'd be cowering down in a basement somewhere hoping not to be noticed!