"To My Nine-Year-Old Self" is written in the form of a dramatic monologue delivered by an adult woman speaking to her nine-year-old self. The setting of the poem is metaphorical; the speaker is not literally traveling through time, but rather is envisioning talking to the girl she once was.
The speaker begins with asking her younger self for "forgive[ness]" for intruding upon her. The speaker therefore recognizes that she is an unwanted adult presence in the mind of her younger self. Kids are often squirmy when under an adult's gaze, so this response seems normal! And while the speaker recognizes her younger self, she is a stranger to this nine-year-old girl. The speaker therefore tells her younger self not to "look so surprised, / perplexed, and eager to be gone" as she wants to her younger self to remain and listen to her.
The speaker then quickly establishes her intimate knowledge of her past self. She knows her past self might depart "balancing on [her] hands or on the tightrope." This imagery in line 3 depicts the nine-year-old self's character and personality as playful and fearless, as her younger self is unafraid of falling and potentially getting hurt. These difficult and strenuous acts of balance also imply that the nine-year-old's body is fit, limber, and energetic.
The speaker goes on to list her younger self's preferences as she would "rather run than walk, rather climb than run / rather leap from a height than anything." The acts of running, climbing, and leaping again suggest an enthusiastic and playful personality, as well as a physically fit body. These acts build up in intensity, underscoring the younger girl's bravery and enthusiasm. Moreover, the younger self does not simply like to leap from a stepping stone or across the grass, but rather "from a height" despite the danger. Thus, the imagery in lines 4-5 continues to develop the nine-year-old's distinctive and fearless character.
Additionally, the repetition of "rather" at the beginning of the clauses in lines 4-5 is an example of anaphora. The anaphora reflects the building intensity of these actions and provides a sense of rhythm to the lines, much like the rhythm that exists in the acts of running, walking, and climbing. The enjambment at the end of line 4 also speeds up the poem for a beat, reflecting the burst of energy required for running and leaping:
... rather climb than run
rather leap ...
The poem is not written in any particular form, meter, or rhyme scheme. Rather, the poem is written in free verse. This lack of form and structure mirrors the free-spirited nature of the speaker's nine-year-old self, whose world the speaker and reader now inhabit.