I think this is a great question and a great goal.
My mother was sick when i was growing up and it did occur to either of us that one day the very similar thing that she had would happen to me- i had boundless energy back then. Would have helped to know it could or woud it just make us paranoid and missing out on activites? I think the former, in my case anyway.
Was only relatively recently i realized that I have had mast cell activation syndrome, or something similar that doesn't have a name yet, likely my entire life. Ditto my mother. Was the last piece of the puzzle and its funny how despite so much research, things you've gotten used to from a young age (when healthy) you don't realize was actually a part ofthe picture of why you got sick later. Forest for the trees issue maybe or you can't cut your own hair issue and one of the reasons i believe each of us needs to view the symptoms as a whole in others becasue you can't do it for yourself when youre steeped in it- but i'm really digressing here.
ok, so in the context of mast cell disorder, i do indeed believe there was stuff i could have done and believe firmly i could have lead a pefectly normal life and not gotten sick had i taken precautions. In my case, it was "allergies" (now realizing of course mast cell reactions) to exentensive dental work (13 teeth , a zillion chemicals, including Dycal in every tooth, a product conttaindicated in those with sulfonamide allergy,) that triggered my ME. At first i recovered from the mystery symtpoms after 1 year, and then a few years later after the next dental work, it triggered it again and my disease was permanant and also lead to autoimmune disease).
So i think maybe for those who also have a disease that goes along with ME and occurs first, those people should be on alert that these disorders put one at higher risk for ME and can take precautions. For mcas, that would include avoid onslaught of chyemicals all at once, try out a small dose for a week to test for reactivity before letting anyone do anything, anything you do should be reversable, assemble a battery of antihistamines etc that you can tolerate and use during any avoidable exposure, don't use pesticides in garden, all indoor clearning products should be mild natural things (i.e. things you could EAT and not get sick). All these should be done from whenever when suspects one has this, often in childhood, and preferably long before getting sick. )
So i think at least in some cases, yes, people can do things to prvent getting CFS/ME