Where did their misery simply drain away? Their heart-rose is now swaying.

This beautiful couplet paints a picture of a profound change. It asks, "Where has all their misery and helplessness gone?" The answer is implied: "Their heart, like a blooming rose, is now swaying with joy." It suggests a wonderful transformation where past struggles and sorrows have completely vanished. In their place, the person's inner self is now vibrant, full of life, and blossoming with happiness. It speaks to a deep sense of peace and contentment found after overcoming hardship, where the heart metaphorically blooms and dances with renewed spirit.