The speaker is having a terrible day, and the bright weather only makes it worse. Right away we get a pile of raw feelings: longing, anger, rage, and a strange mix of desperation and boredom. The "sunshiney" day, with its quotation marks, sounds almost sarcastic, as if cheerfulness is something being forced on them. "I don't want it," they say flatly.
What they want instead is "deranged jottings," messy and unfiltered writing. The question about how to stop envying "the beloved's life" suggests jealousy and loneliness, though the poem doesn't explain why. Lying flat on their back and cursing the gods, the speaker's mind fills with noisy images: cat claws, a "POW," screeching, dying mice. Then comes the grand, half-joking phrase "General Misery / advancing on Saigon of the Soul."
The mood is restless, bleak and oddly playful. The last line, "Yes, let's have / that, too," turns despair into a kind of dark acceptance, as if the speaker decides to let the misery come in.