The title points to Ash Wednesday, the day of ashes and mortality, and the poem opens with ash taking over the speaker completely. Joy shrinks to "only a seed on the wind," something tiny and easily lost, though a seed also hints that it might land somewhere and grow.
What the speaker does next is oddly ordinary and a little absurd. They head to the alley and buy a cat and a good piece of cheese, as if grief could be handled by shopping. The admission "I wonder why" is honest and slightly bewildered; the speaker doesn't fully understand their own impulse.
The last two lines give the closest thing to an answer: "As if it is better to be here / than anywhere else." The "as if" keeps it uncertain. The mood is quiet, wry, and tender. Sadness is real, but so is the pull toward small comforts, warm fur and good food, that keep a person tied to the living world.