I don't really think this is a question that a normal, loving, parent can answer because I think most parents would say that their child's good health and happiness are equally important to them. It goes without saying that parents want, first and foremost, their child to be healthy. Being healthy is a big part of also being happy. Being/staying healthy also involves a certain amount of awareness of reasonable safety rules. There's "safety" as in encouraging children to, say, be active and have fun. Then there's "safety" as in eliminating, as much as possible, the chances that some freak will steal one's child and do horrible things. That kind of thing can pretty much assure that the child will never be truly the kind of happy that he otherwise might have been.
So, to me, a few not-quite-applicable other ideas/sayings/questions come to mind, like the question, "When did you stop beating your wife?" or maybe the saying "comparing apples to oranges" (or else, maybe more applicable, choosing one "more important" apple from a bunch of very similar ones, and "comparing apples to apples - sort of, but not exactly". :/
One of the biggest things being a parent teaches us is that SOME issues/questions that were once (and within the context of not being a parent) fairly "black-and-white" just aren't so black-and-white once a person is a parent and must make some decisions/choices in an attempt to safeguard the mental, emotional, and physical well-being of the child.
For me, personally, I'd need to know the exact situation, age of the child; and individual child, himself, in order to make some choices about "safety-versus-happiness".