Four short lines, and a whole sting of disappointment packed into them. The speaker has had a dream that felt lovely, one about another person, "you," doing things that person would never do in real life. The dream gave the speaker something waking life doesn't, and the gap between the two hurts.
The feeling is wistful and a little bitter. "Shame on the reality" is a blunt, almost sulky line, as if the speaker is scolding the real world for failing to measure up. The poem doesn't say what the "you" did, and that silence matters: we're left to imagine something tender or longed-for, which makes the loss feel more personal. The rhymes ("me" and "reality," "you" and "do") give it a simple, song-like rhythm, but the mood underneath is sad. It captures that familiar moment of waking up, still warm from a dream, and realizing it was only that.