1) This poem by Emily Dickinson explores the impossibility of the speaker living with her beloved. She considers and rejects a variety of possibilities - living together, dying together, being reunited in heaven - finding each possibility barred due to the limitations of their earthly existence.
2) The speaker implies that living with her beloved would be like eternal life, which is symbolized by the Christian ritual of communion, and such a fulfillment could challenge God's paradise.
3) In the final stanza, the speaker accepts that they "must meet apart," separated by vast distances like oceans, communicating through prayer and sustained by the "white sustenance" of despair.