What idea do these quoted lines carry?

“ For oft, when on my couch I lie In vacant or in pensive mood, They flash upon that inward eye Which is the bliss of solitude; And then my heart with pleasure fills, And dances with the daffodils. ” 
What idea do these quoted lines carry?
【正确答案】：

THE EMPTINESS OF THE SPEAKER’S SPIRIT IS TRANSFORMED INTO A FULLNESS OF FEELING. IT IS GREAT BLISS TO RECOLLECT THE BEAUTY OF THE NATURE IN TRANQUILITY.

【题目解析】：The emptiness of the speaker’s spirit is transformed into a fullness of feeling. It is great bliss to recollect the beauty of the nature in tranquility.