It's far more luck than anything else.
Is the term fundamental attribution bias? I can't remember, it's something like that -- the tendency we have to overestimate the role our behavior plays in a situation and underestimate external factors. You can run all the marathons you like and micromanage every fucking nutrient that enters your body, but if you come across the wrong pathogen, or have a gene that's just a little wonky, you're fucked.
ETA: Fundamental Attribution Error -- I was close!
I agree with you, but if you get hit with a pathogen or develop cancer and you've let yourself fall into a state of lifestyle induced ill health dealing with disease will be a lot harder on you. And that just plain applies to age as well.
If you say, "I've got my health" that's luck.
If you say, "I've worked to maintain and achieve this level of physical well being" that's success.
I do agree with that, sort of. However the converse is that if one starts qualifying health in terms of success, then when things don't go so well, one feels a failure. I guess my particular disease is just exceptionally apt for illustrating how little control we actually have over our bodies, which made the inaccuracy of that statement stand out especially. I can do absolutely everything
perfectly: dose exactly right at the exact right time, eat exactly the right amount of exactly the right foods, cover exactly for whatever physical activity I'm doing, and still some other confounding factor will come in and fuck up my blood sugar. It's not a reason not to keep working at it, but it's a very good argument against seeing health as something at which one can be successful. We may be successful at certain behaviors which can promote good health, but that's not the same thing as being healthy.