That's a beautiful poem that I never read. I would say that she's talking about how closed off and hollow we all feel until we actually fall in love or recognize that we love and are loved by another. Then when we give our hearts to someone, we become incredibly vulnerable and open ourselves up for unknown pain--their problems, ours--maybe even the loss of the loved one, but it's all worth it ultimately because life is meaningless and empty without love of something or someone, imo.