The "inward eye" the poem's narrator speaks of in the last stanza is memory. In this final stanza, the narrator also says that often when he is lying on his couch in a "pensive" mood, his mind flashes back to the dance of the daffodils he saw on an early spring day. This memory gives him happiness. Wordsworth writes,
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.
One of the goals of Wordsworth had was to write poems about emotions he experienced as he recollected them in a more tranquil state. At the end of the poem, the narrator is tranquilly recapturing his emotion of pleasure at the sight of the daffodils. Since Wordsworth wrote a poem about the joy the daffodils gave him, the rest of us, even if we have not seen such a sight, can imagine the daffodils with their yellow heads gaily dancing in the breeze in front of a sparkling lake. We too then can participate in the pleasure.