I agree with this. When people are young, especially, they need to vary things quite a bit until they find what works best for themselves. This is especially true when we consider the best ways to stay healthy. AND...that does not necessarily equate with staying "fit." Many "fit" people have died young from lack of proper nutrients, or bad habits in other areas of their lives, or from stress.
For me anyway, and speaking for no one else, I haven't been to a doctor for 20 years and am 57, and quite healthy, despite being overweight. What works for me is ROUTINE, strangely enough, especially in my dietary regimen and vitamin/supplement intake. I swear by Vitamin D3, for example, and have not had a cold since I started taking it regularly 15+ years ago now. That is just an example, but I also believe in supplements such as turmeric, cayenne, cinnamon, ginger, nigella seeds, and quite a few more. I ingest these daily, and take lots of other vitamins as well.
I should exercise more, for sure though, and I am working on that...
Great post, by the way!