In "I Wandered Lonely as a Cloud," how does Wordsworth challenge owning things?

I interpreted the original question in another way. I thought it was asking how the narrator was able to change his own thinking (not things) during the course of the poem. Here’s an answer.

In the opening scene, the narrator is walking by himself and rather aimlessly, since he compares the action to the movement of clouds. The impression is one of solitude with a hint of sadness. You can imagine shades of gray too,...

I interpreted the original question in another way. I thought it was asking how the narrator was able to change his own thinking (not things) during the course of the poem. Here’s an answer.

In the opening scene, the narrator is walking by himself and rather aimlessly, since he compares the action to the movement of clouds. The impression is one of solitude with a hint of sadness. You can imagine shades of gray too, with the cloud simile. Then he comes upon the field of daffodils. The yellow flowers are bright, cheery, and welcoming; and they offer a completely different scene and mood. You can’t help but be happy, just by looking at them (“A poet could not but be gay, / In such a jocund company”). This sight improved the narrator’s attitude immediately.

But Nature had even more inspirational power for him, and one that lasted longer than just that one day. Now he discovered that whenever he felt sad or low or depressed (“In vacant or pensive mood”), he could remember the daffodils and make himself happy again. He could improve his attitude, just by thinking of that yellow landscape. If you were asked to think of a happy scene or time from your past, what would it be? Does it still cause you to smile or laugh? Then you know how this technique can work. For Wordsworth’s character – or for the poet himself – the triggering thought was of the daffodils.