I love how a poem, an essay, or a novel can shimmer with new meaning when you reread it years later — when the defining moments of your own life realign with the story. It’s a bit like running into an old friend who looks better as he ages. I first read Billy Collins’ “Forgetfulness” in Questions About Angels more than 10 years ago. This week, while thumbing through Collins’ anthology, Sailing Alone Around the Room, the poem found me again. And this time my heart jumped as I read the line, “one by one, the memories you used to harbor decided to retire to the southern hemisphere of the brain….”…