Personally I didn't do a lot of fun stuff (like riding motorcycle, extreme sports) to decrease probability of an accident, even though I'd love to (I'd tried them, loved doing them, but not doing them regurarly).

As for cancer and heart disease, both are linked to aging or genetically inherited mutatations. Heart disease is a natural result of damages in the human body not being reversed.

https://www.cell.com/fulltext/S0092-8674(00)80567-X