My heart, I cannot still it,
Nest that had song-birds in it;
And when the last shall go,
The dreary days to fill it,
Instead of lark or linnet,
Shall whirl dead leaves and snow.
The speaker compares his heart to an empty nest in order to
He is comparing his heart to an empty nest because he feels alone and depressed, sort of like a feeling of dreary emptiness when viewing a picture of an empty nest.
