In her third and latest memoir, “New Life, No Instructions,” Gail Caldwell offers the kind of wisdom and grace you’d wish a friend, sister, or mother might deliver when you’re circling the drain. “Any change that matters, or takes,” she explains, “begins as immeasurably small. Then it accumulates, moss on stone, and after a few thousand years of not interfering, you have a glen, or a waterfall, or a field of hope where sorrow used to be.”