Final answer:
Without exact reference to complete the verse 'When these things begin to...', an accurate finish cannot be provided. The given excerpts do not include a direct continuation but suggest deep literary engagement with life and existence.
Step-by-step explanation:
The verse, "When these things begin to..." seems to require completion; however, none of the provided excerpts seem to finish this verse directly. It is plausible that the verse comes from a piece of literature or poetry not included in the given references. Without the proper context or additional information, providing an accurate completion or reference is not possible. Nevertheless, analyzing the given excerpts shows the thematic essence of contemplation on existence, life's cyclical nature, and introspective contradictions, which are common in poetic expressions. This reflects a deep engagement with the world and an understanding of life's complex intertwining of experiences. For example, the excerpt discussing the contradiction, "Very well then I contradict myself," from Walt Whitman's "Leaves of Grass" emphasizes the complexity and multifaceted nature of the human condition. Each selected passage represents an invitation to reflect deeply on life and existence, whether through experiencing nature's beauty, pondering philosophical questions, or recognizing the multi-dimensionality of the self.