The natural world and the art of poetry are a big deal to our speaker largely because they can impart profound, transformative experiences. They can transform how we feel and how we understand the world. Of course, our speaker suggests that profound experiences require work on our part, but if we build our attention and open-mindedness, they will come.
Section 1, Lines 2-3: Metaphor is one of the primary transformations of poetry, and this one conveys the way a sunrise can transform the bodily experience of the speaker—the spread of sunlight feels like a rinsing or cleansing. Powerful stuff.
Section 1, Line 5: So we're going to call this an implied metaphor within a denied metaphor. What in the world are we talking about? Well, this line is given to us in the form of "Thing 1 is NOT thing 2," which is like saying "Hey look, this is not a metaphor!" But within that denial of a metaphor is a metaphor, or the suggestion of one. Now maybe a rain-purse is just something we've never heard of, but we think there's a transformation implied, too: the rain is being equated with change being poured out of a purse. Our idea of God, too, has to be transformed a bit to accommodate a purse.
Section 2, Lines 8-10: Our speaker uses anaphora (repetition) to transform our perception of this scene in the barn. Using that phrase "Mostly, though" a second time is kind of like taking a step back and seeing or experiencing the barn from a whole new angle. Normally we expect that if something is mostly one thing, it can't be mostly another thing as well, right? But what most affects us from moment to moment can change, and this transformation of what the barn "mostly was" reflects that.
Section 10, Lines 1-5: We think this is a rhetorical question. The purpose seems to be to impress upon us the importance of finding something in world, or the proper approach to the world, that will open us up to transformative experiences.
Section 8, Lines 3-4: This doesn't necessarily have to be personification (we could call it animation), but our speaker is definitely lending living, brain-requiring attributes to what we think of as a decidedly non-living thing: a poem. The effect is to transform the poem from a flat, inanimate collection of words into something with a will, and the ability, in turn, to transform us.