Grace's speaker lives behind walls of their own making. People are all around, but their thoughts feel blocked off from everyone else, and even from themselves. The line "And I away from Myself" suggests the isolation goes deeper than being apart from others: the speaker feels cut off from who they are.
What makes the poem stand out is the reason given. The speaker isn't simply lonely or shut out. They believe solitude is necessary "to protect them from me." Loneliness here is a sacrifice, though it may also be a painful belief the speaker has settled into. Nobody understands this, which adds another layer of distance.
The mood is heavy, quiet, and resigned. The short, broken lines feel like someone speaking carefully, almost out of breath. The repeated "I must always be alone" closes the poem like a door shutting, leaving us unsure whether the speaker is truly protecting others or trapping themselves.