"Sometimes" describes a sudden slide into despair. The speaker is fine one moment and overwhelmed the next, and the plain phrasing, "Just like that," makes the change feel abrupt and unavoidable. The mental storm doesn't stay in the mind, either. It spreads into the body, leaving the muscles aching and the limbs heavy, as if the emotional weight were physical.
What stands out most is the speaker's isolation. They keep their struggle hidden, convinced it would only burden others, and even call it "pointless shit" they can't make sense of themselves. That self-dismissal shows how lonely and ashamed they feel. The short lines and the single word "Alone." leave the poem feeling bare and still.
The closing image, the body as a coffin with the speaker buried alive, pulls everything together. It suggests being trapped and unheard, still living but cut off from everyone. The mood is heavy, quiet, and painfully honest.