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.