Why are the last two stanzas of "Still I Rise" different from the rest?

Most of the first seven stanzas of Maya Angelou's poem "Still I Rise" include mention of a second-person character ("you") who oppresses the narrator. The "you" the narrator addresses is the white male world that has oppressed the narrator and tried to negate her humanity. The first seven stanzas (with the exception of the third stanza) catalog some of the ways the white male world has tried to make the narrator powerless, including telling "bitter, twisted lies" about her and being offended by the narrator's pride in herself, including her "sassiness" and her "sexiness." In each of these stanzas (except the third), the narrator carries out a kind of metaphorical battle with the "you" who would like to reject and deflate her. Each of these stanzas is four lines long, and in each stanza (except the third), the second and fourth lines rhyme.
The last two stanzas are different in form and content. They are six and seven lines long, respectively, and they do not include any reference to "you." Instead, they feature ways in which the narrator will rise and include the repetition of the line "I rise." They also often begin with "I," stressing the power of the narrator to overcome all the oppression she has been subjected to. These lines are hopeful, as the narrator says she will rise "Into a daybreak that’s wondrously clear." In the last two stanzas, the narrator has broken free of the oppressive past and entered a hopeful future. 

The last two stanzas of Maya Angelou’s poem “Still I Rise” change in purpose and tone from the first seven stanzas. After the first stanza, the poem becomes interrogatory, with the narrator asking a series of provocative questions. She implores readers to consider her “haughtiness” and “sexiness,” and asks if their feelings are stirred by her ability to overcome endemic and pervasive prejudice. In the final two stanzas, she stops questioning the reader and emphatically states her case.
In the final two stanzas, she describes the inner fortitude which allows her to “rise” above the atrocities she and her ancestors endured. In addition, she describes her actions as breaking the bonds for future generations. She does not question this; she declares it to be true.

I am the dream and the hope of the slave.
I rise
I rise
I rise.