This poem is essentially about Dickinson's wish for her poetry. If you look at her life, she was very secluded and very isolated in nature. Her body of work was enormous and really, that was all she had. I've always looked at this particular poem as an answer to someone who had questioned her about why she wrote. She had such a clear understanding of humanity, yet she was so isolated from it herself. This poem serves as a response to those who questioned her motives.
I think her love of nature is also shown in this poem. While she didn't write for the "fainting robin," animals certainly served as characters or references in many of her poems.