The luster of tears fades away, just as a lamp goes out when all the oil is consumed.

This couplet uses a beautiful metaphor of emotional depletion. The poet suggests that tears are like a lamp's light, and the sadness or pain is the oil. When one has cried until the last drop, when the source of suffering has been completely drained, the tears naturally stop. It speaks to a profound emotional exhaustion—the moment when the heart simply runs out of capacity to grieve.