Ibsen's play ends with Nora deciding to break up her marriage, leave her husband and children, and go off on her own. She hopes to develop an identity of her own. This decision is the surprising culmination of Nora's conflicts, both internal and external.
Over the course of the play Nora faces challenges to her honesty, her willingness to face up to her own actions (moral, immoral, loving and criminal), and, finally, challenges to her sense of self. The breaking point for Nora comes when Torvald fails to do the "miraculous thing" that she expects of him.
When she tells her husband about Krogstad and the loan, Nora expects that Torvald will offer to take the blame himself. She expects him to be both noble and loving. If he were to act in this way, Nora's view of her marriage would be reinforced and she would even be personally redeemed.
Torvald does not act in this way. To the contrary, Torvald berates Nora and shouts at her about how she has ruined him. It is this behavior from her husband that opens Nora's eyes to the truth of her marriage and forces her to face the difficult truths that A) Torvald has no respect for her and B) she has no identity of her own.
Her problem is that she is totally dependent upon her husband for all her needs; or she deceives herself into thinking so until the end of the play.
Nora attributes this fact of her character to the treatment she has received from both her husband and her father.
Nora's personal crisis leads to a major decision for her future and for the future of her family. She decides to leave her husband and children. Torvald tries to convince Nora that he now understands how he should treat her. He tries to convince her to stay, but she is adamant about leaving.
Her decision to leave is a daring one that indicates the seriousness of Nora's desire to find and create her own identity.