Sam/Dean/Claire.
They never do. They're run by morons.
I was. I mean I had the genes or whatever. But I think my body matured to peak physical fitness and then, kinda stayed there. Or there was an eclipse that kick started it into what it is now, but I was never sick as a kid or anything.
Oh right and eclipses. Not fun for me. Nearly died last time.
Its alright, its not your fault and I've pretty much accepted this is my life whatever dimention I wind up in.