The presence of the lyric in contemporary poetry is of considerable interest because it provides new solutions to the question “of how the “lyrist” is possible as an artist.” One of the things the lyrist-as-artist manages to do is to convey intensely personal feelings musically, without making us cringe (the opposite of which happens so often at poetry readings). We can ask how the lyrist manages to do this, and Nietzsche gives a theoretical explanation based on his hypothesis of two art impulses in nature: the Dionysian, which is the mystical feeling of oneness with the world; and the Apollonian, which is the joyful experience of the world as appearance or dream. For Nietzsche, the lyrist (of the Greek tragedies and dithyrambs) is someone in whom both the Dionysian and Apollonian impulses converge. The Dionysian drags him into a dizzying, ecstatic and painful identification with everything in the world—to the extent that the subjective vanishes into “complete self-forgetfulness [p 4]” —while the Apollonian ejects him out of this terrible picture and redeems him with the ability to view it as a dream:
“The artist has already surrendered his subjectivity in the Dionysian process. The picture which now shows him his identity with the heart of the world, is a dream-scene, which embodies the primordial contradiction and primordial pain, together with the primordial joy, of appearance. The “I” of the lyrist therefore sounds from the depth of his being: its “subjectivity,” in the sense of the modern esthetes, is pure imagination. [p 14]”
Never mind the theoretical apparatus, Nietzsche arrives at a simple though startling conclusion: the “I” of lyrical poems is a fiction. And it is startling for precisely this reason: when the artist is most personal, he is not himself.
 p 13, The Birth of Tragedy, Friedrich Nietzsche, Dover Publications, 1995.