The primary focus of John Keats' poem "When I Have Fears" is the fear of running out of time, which leads, eventually, to death. Other fears the poet addresses are of not experiencing love or beauty and of not seeing his work published.
The poet is attempting to face his most terrible fears. The most significant fear he faces is death, which creates another fear, that of running out of time. The thought of running out of time triggers further thoughts of dying before he can get the ideas that are in his head written down on paper or before his ideas and poems are published.
When the poet looks at the night sky, he is not only afraid he may not experience love or beauty, but he is afraid that he may never be able to solve such mysteries. He spends a lot of time contemplating love, which makes him think of his heart’s love, Fanny Brawne, whom he fears he may never see again. He notes that he may never “relish in the faery power of unreflecting love,” which is almost more than he can bear. The final lines indicate that the poet snaps back to reality out of his meandering daydreams and faces his fears alone.