In the first paragraph, Miss Brill seems quite cheerful on the whole. It's a fine, sunny day, with the bright blue sky adorned with pretty little spots of light. There's also a slight chill in the air, but that gives Miss Brill the opportunity to dust off her fox stole and wear it on her day out at the park. She seems to feel genuinely thrilled at the prospect of draping the fur across her shoulders once more. It's nice to feel the little creature again; and those eyes of his are so sweet as they stare at her.
Despite Miss Brill's apparent cheerfulness, we sense immediately that there's something empty, something lonely about the life she leads. In the first paragraph she talks about her fur as if it were some kind of pet, a living creature. And when she breathes, something light and sad—something gentle—seems to move in her bosom. It's as if the novelty of wearing the fur once more has suddenly worn off, and she's been forced to confront the chronic loneliness that characterizes her drab existence.