In the first line of the poem, the darkness is something that we are already growing “accustomed” to. Seems like we’ve been hanging out in the dark for awhile, then. Later on, in line 7, we step out from a lighted room and into the night and must again adjust. But shortly after this imagery, Dickinson gives us a hint that this darkness isn’t totally literal; in line 9, she mentions a “larger Darkness” of the mind. Darkness is serving as an extended metaphor of the unknown; not even the light from the moon or the stars are around to help out. At the end of the poem, the “bravest” among us put aside their fear of this unknown and walk into the “night” to face it. By doing this, they adjust to the unknown and it becomes easier to see what lies on the other side.