QUOTE : He asks, “Is this remorse, Severus?” Snape doesn’t reply. He doesn’t understand yet what Dumbledore means. Instead, he says he wishes he were dead. (HP/DH, 678) He is quite sincere. His life is over. From this point on, if Dumbledore intervenes and calls on the most vital thing remaining in Snape—his love for Lily—Snape can start again, from the beginning, and have a second chance to do right. It is too late to protect Lily, but if all goes well, Snape can help spare the innocent life of Lily’s son, whom Voldemort will surely attack again. Snape cannot live for himself anymore; his heart is broken by guilt; he doesn’t feel deserving. But he gave himself to Dumbledore when he pledged “anything” in exchange for Lily’s protection, and Dumbledore sees a hope. If he calls on Snape to live for Dumbledore for the moment, to do as Dumbledore orders him, and keeps calling on the part of Snape that loves, keeps calling on Snape to do more and more for love and protect others for love, there’s a chance that this love can grow strong enough to sustain Snape so that he can find his own reasons to live again.