That’s an interesting question and there isn’t a universal answer to it. Health is a complex puzzle, and what you consider the most important part of your health may not be what others value most. For example, in my case as someone who enjoys writing, games, and movies, the worst fate for me would be losing my cognition over the years. Because of that, I should make sure to keep exercising my mind and socializing to decrease my chances of dealing with severe cognitive decay.
However, your main priority might be wanting to make sure you can still get around on your own even in your silver years. And in that case, your focus should be on exercising and weight management, so you’ll be able to avoid landing on a wheelchair for as long as possible.
Of course, it makes little sense to focus on maintaining only one aspect of your health as you age. You should be looking after your health in general, which you can do by looking after your body, mind, and by staying informed with the help of platforms like SuperMedical.