The speaker describes seeing patterns everywhere: on the walls, the floor, the ceiling, the door. The opening lines repeat "I see them on…" over and over, which makes the visions feel constant and inescapable. The speaker admits not knowing why this happens. Sometimes the patterns are frightening, and sometimes they seem "quite merry," so they aren't simply good or bad. They even seem to speak, "trying to tell" the speaker things.
The tone shifts in the last four lines. The speaker mentions that a doctor said it was "fine," which sounds a little reassuring but also a little dismissive, as if the speaker is left to cope alone. Then comes a surprising turn: the patterns teach the speaker how to write poetry, though not how to rhyme. That last line is playfully humble, and it adds a note of humor. The mood moves between unease, curiosity, and a wry, almost cheerful acceptance.