Certain phrases cycle in and out of child-rearing vogue, with “executive function” and “emotional intelligence” and “kinetic learning” zooming before parental headlights and then passing into oblivion until the next generation comes along. At our current moment, “resilience” is front and center, in large part courtesy of Paul Tough’s excellent book on education, “How Children Succeed.” And to this parent, at least, it seems as good a concept as any to cling to and to encourage.