Four short lines tell a small, sad story about what happens when you try to possess something wonderful. The speaker describes a person, addressed as "you," who had a kind of magic that other people wanted to take for themselves. The word "steal" suggests this quality was rare and attractive, something people were drawn to and hoped to claim.
The turn comes in the last two lines. The speaker, who seems to have been different from the others, decides to become a thief too, and the magic disappears. The poem doesn't spell out why, but the idea feels clear: some things only exist as long as they're left free. Once someone grabs at them, they vanish.
The mood is quiet and regretful. The speaker sounds less like they're blaming the other person and more like they're admitting their own mistake, with the loss arriving almost like a confession.