The Child is father of the Man (7)
The speaker puts a lot of stock in childhood. This line is a paradox, taking what we normally think about identity and setting it firmly on its head. We tend to think that children get their identity from their parents, but this suggests that as adults we are shaped by our childhood selves. Our speaker's love of nature as a child turned him into a nature-loving adult.
And I could wish my days to be Bound each to each by natural piety. (8-9)
The speaker sums up the poem with a statement about what he wants his identity to be: he wants every day of his life to be connected with nature. The word "pious" implies that our speaker wants to be dutiful and reverent toward nature. He digs it so much that he defines his entire identity around nature and his ability to experience joy through it.