amy-lepore makes a good point, but I think it goes a little beyond that. Writing was something which she enjoyed and which fulfilled her. However, the men in her life diminished the importance of this activity. That's when it started to affect her happiness. Even when she was doing it secretly, she didn't have the same happiness as she did before they suggested she stop.
The narrator is happiest when allowed to write. Once her notebook is taken away and she is no longer allowed this outlet for her thoughts and sanity, she takes a nosedive into the insanity that drives her to crawl around the room and over her husband's body.
The narrator does go through several stages as she decends into madness. At the beginning of the story, she is suffering from, most likely, post-partum depression when her husband locks her away. As she begins to notice the specifics of the room, things begin to fall apart for the narrator. She gradually, then, becomes obsessed with the wallpaper and its pattern. Then, she noticed a woman in the wallpaper and her narrative begins to ramble a bit. Her writing becomes more disjointed instead of clear. She goes against her husband's wishes to limit writing in her notebook, as well. Later in the story, she becomes obsessed with the wallpaper and the woman she believes is in the wallpaper. This truly represents her decent into madness, which ends with her crawling around the baseboards of her room and over her husband, who has passed out when he comes in the room and sees what the narrator is doing! In her own mind, the narrator is free of the confines of the wallpaper once she has torn it down and she is almost giddy at the end of the story. Very strange, indeed.
The poor narrator is confined by her physician husband to a room, forbidden to read, write or engage in any stimulating activity. She is remanded to total bed rest to ease her condition of post-partum depression after the birth of her son.
With little choice, under the close supervision of both her husband and her sister-in-law, the narrator, who believes that work, excitement or a different setting would help cure her, she is stuck in her room. Restricted from enjoying the gardens, or the outdoors in the beautiful country where the house is located, the narrator begins to focus on the wallpaper in her room
"This wall-paper has a kind of sub-pattern in a, different shade, a particularly irritating one, for you can only see it in certain lights, and not clearly then." (Gilman)
She begins to believe that there are things hiding and living within the pattern of the wallpaper. She sees a woman in the wallpaper who she believes is trying to escape. She becomes fascinated and fixated by the challenge of helping the woman in the wallpaper escape.
"This trapped figure symbolizes the narrator's emotional and intellectual confinement. Left with no real means of expression or escape, the narrator represses her anger and frustration and succumbs to insanity."
''The story traces the narrator's gradual identification with her own suppressed rage, figured as a woman grasping the bars of her prison and struggling frantically to get free.''