Miss Brill's mood at the beginning of the play is one of trying to pump herself up to be happy. She tries to hide her sadness from herself. She focuses on the bright side of life: the beautiful day, her upcoming outing to the park, and wearing her beloved fox fur around her neck, a carefully preserved piece of clothing which she carefully brushes. Yet hints that she is sad appear from the start:

something light and sad—no, not sad, exactly—something gentle seemed to move in her bosom.

As she goes to the park, she exhibits, internally, a desperate gaiety. She finds happiness in sitting in her usual place on a park bench, enjoying the band playing, and eavesdropping on the conversations around her. She pretends she is an actress with a part in a weekly play and thinks,

Yes, I have been an actress for a long time.

Miss Brill even perks herself up by finding happiness in whether or not an almond is in the slice of honey bread she buys for herself as a treat every Sunday.

By the end of the story, however, Miss Brill can longer keep up the façade of happiness. She can no longer be an "actress" when she overhears cruel comments from two young people who don't want to sit near her:

"Why does she come here at all—who wants her? Why doesn't she keep her silly old mug at home?"

"It's her fu-ur which is so funny," giggled the girl. "It's exactly like a fried whiting."

This shatters her and brings home to Miss Brill that she is just like other old people sitting on the park benches like statues in faded clothes, as if they have come from tiny rooms or cupboards. That is her life, too: she is old, poor, sad, and lonely. She hurries past the bakery and back to her room, which she admits is as small as cupboard. She quickly puts her fox fur away but thinks it sounds like it is crying: in fact, it is Miss Brill's soul crying at her unhappy life.

At the beginning of the story, Miss Brill is in a cheerful, upbeat mood. She is looking forward to taking her weekly trip to a concert in the gardens. In preparation for the outing, she takes out her old-fashioned but well-loved fox fur and then heads to the gardens. She looks forward to hearing the music, but even more so, abating her loneliness by overhearing the minutiae of the lives of some of the people around her. She focuses on the people around her intensely, as if using the powers of observance which have no use in the rest of her life.

By the end of the story, however, Miss Brill is feeling crushed, dejected, and lonelier than ever. The reason for the change in her mood is the arrival of a sophisticated young couple who made no effort to lower their voices when referring to Miss Brill as a "stupid old thing." The girl expresses her displeasure at the idea of sitting anywhere near Miss Brill and verbalizes the opinion that no one wants Miss Brill there and that she should just stay at home.

To an already lonely Miss Brill, these words are obviously devastating. She has been an object of ridicule and judgment, and the degree to which she is upset is shown by her skipping her usual stop at the baker's on her way home.

It's fair to say that Miss Brill lives for her weekly visits to the park. They give her a chance to indulge in her favorite activity of people-watching. Each time she goes to the park, Miss Brill creates her own little theatrical fantasy world in which the people she observes so intently play bit parts.

As someone who lives on her own and clearly doesn't get out all that much, Miss Brill looks forward to these weekly excursions, not least because they give her a sense of power and control in her life that would otherwise be absent. Among other things, this makes Miss Brill rather happy, and she certainly seems to be in a good mood when she rocks up at the park for her latest outing.

However, thanks to the hurtful, insensitive remarks of a young couple nearby, Miss Brill's initially buoyant mood is completely ruined, and so is her day at the park. The poor lady trudges wearily back to her sad, empty little flat feeling hurt, humiliated, and embarrassed. For the first time on one of her jaunts to the park, she knows what it's like to be a bit-player in someone else's drama, and she doesn't like it one little bit.

Interestingly enough, there is little affect in Miss Brill's disposition at the start of the story and at the end of it.  In the beginning of the story, she sees herself as the center of all attention, the reason for being in the world.  She envisions herself as what Mansfileld would describe as a "conductor" or as some type of director who is designing and configuring a setting that she herself controls.  For whatever reason, she feels a part of what is happening.  At the end of the story, there is little reflection or emotional affect to the couple's comments.  She did not get herself the small treat at the bakery she normally does.  When she goes home, she blames the stole for what happened.  One notable change is that the fur that she revered at the start of the story is what she ends up blaming at its end.  Yet, there is little change in her and in how she sees herself.  The mood at the start of unrerpressible joy and zeal is replaced by a sense of blame at the end.  Yet, Miss Brill, herself does not seize the moment to reflect inwards. Rather, she displaces her own need to personally reflect by blaming the fur.  In this, there is change in the mood presented because what was once there at the start is different at the end.  Yet, she, herself, as a character is not presented as one that has endured a great deal or seismic sense of change in her own perceptions of the world and her place within it.