I f there’s one thing you can say about Americans at this point in time, it’s that we’re stressed—and we’re constantly told by health experts to reduce or manage our stress because it’s killing us. But what if I told you that stress can actually be good for you—and that, sometimes, more stress is actually helpful.  As a doctor and researcher in stress and healthy aging, I know that sounds nonsensical or, at best, counterintuitive, but that’s exactly what the fascinating new science of hormesis ,