If the crossing of the heart does not happen, what is the nightingale? The stream of the soul is the poet, the beauty of the mood.

This profound couplet speaks to the inescapable nature of deep emotion. The poet suggests that if the heart itself cannot endure the passage of pain, then what is the point of the beautiful song of the nightingale? The ultimate realization is that the very flow of pain—the veins of the heart—are the melody, the inherent tune of existence. It's a beautiful surrender to sorrow.