Final answer:
The phrase in question uses a Metaphor to compare the speaker's existence to a miracle, emphasizing the wonder of one's own being.
Step-by-step explanation:
The excerpt you've provided illustrates the use of a Metaphor. A metaphor is a figure of speech in which a word or phrase is applied to an object or action to which it is not literally applicable, without using 'like' or 'as' (which would create a simile). The phrase 'This miracle of me is mine to own and keep...' suggests that the speaker's very existence or essence is being described as a miracle, which indicates a metaphorical comparison of one's being to something of extraordinary wonder or significance, without a literal connection.