Final answer:
Nora decides to leave Torvald to educate herself and find her own identity, as their marriage made her feel like a 'doll' and she lived with a stranger for eight years.
Step-by-step explanation:
At the end of the play, Nora cites several reasons for leaving Torvald. Foremost, she feels they are strangers to each other after eight years of marriage, which has left her feeling like a "doll" or a "skylark" rather than an equal partner. She tells Torvald that only when the fear for what might happen to him was over did she realize she has been living with a stranger and has borne him three children. This awakening leads to her decision that she must educate herself and find her own identity, which she believes she cannot do while remaining in their marriage. She leaves to stand alone and to understand herself and everything around her, emphasizing the necessity of this journey for her personal growth.