All this starts with genetics and luck of the DNA draw. Diet and exercise come second. However, you can take perfect DNA and sometimes screw it up via lousy habits. You just never know which way the dice will role, although if you have a hacking cough or your pant size is 10" larger than they were when you were 25, your body is telling you a DNA change could be going on, rarely for the better.

Some people can run across a crowded freeway 100 times and never get hit. Others get tagged the 3rd time they try it. Only your DNA knows for sure. Gattaca time.