Focusing on lines 368-73 of the poem., Fredrick L. Hildebrand concentrates on Shelley's use of astronomical metaphors in Epipshchidion--namely, the comet--to help illustrate the poet's spiritual crisis. Hildebrand believes an implicit message of Epipsychidion is that love has the power to control reality for the better. Consider the following passage from Hildebrand's article--"Epipsychidion's Cosmic Collision: A Controlling Metaphor":
It is not surprising to find astronomy providing the controlling metaphor in Epipsychidion, but this poem also contributes some insight into the dynamics which love can control the workings of the universe. Shelley's purpose is figuratively and scientifically to relate people's behavior to their environment in order to dramatize how they can improve their own lives as well as the human condition.The collisions of celestial bodies provide the imagination with possibilities for catastrophe on a universal scale. While planets and stars usually follow harmonious orbits, the paths of comets or errant planets threaten the world with potential disaster. Epipsychidion contains two descriptions of a celestial collision. The more complete version appears after the autobiographical section of the poem. As the poet wishes for the return of the comet to his partially resorted universe, he describes the catastrophe which previously destroyed its harmony. (75-76).
Hildebrand, Fredrick L. "Epipsychidion's Cosmic Collision: A Controlling Metaphor." Keats-Shelley Journal 37: (1988): 75-90.