The human heart (Dom Claude had meditated on such matters) can contain only a certain amount of despair. Once the sponge is saturated, the sea can pass over it without adding one drop more.
From "Les Misérables":
"She has been through everything, borne everything, sustained everything, suffered everything, lost everything, mourned everything. She is resigned with a resignation that resembles indifference as death resembles sleep. There is nothing more she shrinks from, nothing more she fears. Let the whole rain-cloud come down on her and the entire ocean sweep over her! What does she care? She is a saturated sponge."
