Bruce Schneier, a well known security specialist, wrote an essay in The Atlantic that suggests the proper reaction to the attacks in Boston (and other terrorist attacks as well). The essay is worth a full read, but here is an excerpt:
As the details about the bombings in Boston unfold, it’d be easy to be scared. It’d be easy to feel powerless and demand that our elected leaders do something — anything — to keep us safe.
It’d be easy, but it’d be wrong. We need to be angry and empathize with the victims without being scared. Our fears would play right into the perpetrators’ hands — and magnify the power of their victory for whichever goals whatever group behind this, still to be uncovered, has. We don’t have to be scared, and we’re not powerless. We actually have all the power here, and there’s one thing we can do to render terrorism ineffective: Refuse to be terrorized.