The speaker lives with constant pain, and the poem shows how it seeps into everything they see. Even something as ordinary as a dress becomes "blue water," as if the mind keeps drifting back to the ache and tinting the world with it. The speaker admits as much: they cannot keep their thoughts off the pain.
The third stanza makes the suffering feel like unfamiliar territory. Pain is "a new country with no peace," a place the speaker has been sent to, and it troubles them most at night, when distractions fall away. The final lines step back to something larger. The "day of my fall / into this life" is described as old, so the speaker's sense of being born into suffering feels ancient and heavy, not just recent.
The mood is quiet, weary, and a little lonely. The short lines and plain wording make the pain seem steady and unshowy, something endured rather than dramatized.