In the first tercet of "Lady Lazarus," the speaker introduces herself by telling the reader, "I have done it again." Though the reader does not know what "it" is yet, this opening accomplishes two things. First, it establishes the understanding that the speaker is engaged in a kind of cycle (she keeps doing "it again"), and that this cycle has endured across decades. Further this cycle involves something that the speaker wants to do. It's not something she does accidentally. Once every ten years she "manages" to accomplish it.
Once the reader comes to understand that the "it" that the speaker is talking about is her own suicide, the first three lines read differently. First, the poem's central extended metaphor becomes retroactively applied to these lines: the speaker is dead, and speaking as a dead person. Though, since a dead person can't actually speak, this "deadness" is in fact metaphorical. Second, the way that the word "managed" seems wholly insufficient in connection to a suicide—it makes suicide seem akin to getting to the bank before it closes—introduces the heavy irony that pervades the poem.
Line 1 is also the first instance of an end-stopped line, which is used quite frequently in "Lady Lazarus." The line ends with a period: "I have done it again." Here, the punctuation makes the reader take a pause to contemplate, leading the reader to ask, "What did the speaker do?" Although the line is fairly vague on its own, in the context of the whole poem, the end-stopped line contributes to the confessional honesty of the piece— the speaker of this poem has a strong and clear voice, and while the tone of the poem is often inclined towards irony, this speaker also wants the reader to pay close attention and understand her plight.
Lines 1 and 2 are also the first instance of the speaker's use of perfect end rhyme. Though the poem does not have a specific rhyme scheme, many of the lines do make use of end rhyme, either with perfect or slant rhymes. Here, the rhyme of "again" and "ten" assists in establishing the rhythm of this poem, while at the same time the rhyme of those two specific words emphasize both the duration and the repetition of the cycle of "death" and "resurrection" in which the speaker finds herself.