Emily Dickinson uses a lot of imagery and symbols in her poem "We grow accustomed to the Dark—."
First of all, one could argue that the darkness can be seen as a metaphor for the darkness in life, when all hope seems lost. When the poet writes that "Light is put away," one could interpret this disappearance of light as a metaphor for all hope disappearing.
Another symbol that is worth mentioning with regard to this poem is the road. The road could be seen as a symbol for life, as life could be seen as a long road. The road can be dark and dangerous at times, just like the poet is describing at the beginning of the poem. However, once our eyes adjust to the darkness, we can see the road much more clearly. In other words, if we are not too distracted and scared by the difficulties we face in life, the road of our lives will still be there and visible. We need to try to follow it, even when times are tough.
Finally, the "tree" may be referred to as a symbol for obstacles in life. The poet tells us that sometimes we might "hit a tree" during our quest to follow the road in the dark. The tree could be seen as a symbol for the various threats and problems we face in life which might frighten us, hurt us, and possibly even stop our progress. However, according to the poet, it is important that we don't let these problems stop our journey through life. Instead, we should keep persevering despite all of these obstacles, as the poem tells us that eventually things will get better: "Life steps almost straight."