The poem below was a bit hard for me to wrap my head around, so I decided to break it down a little:
I could have borne the shade I could have been able to handle the shade
But light a newer wilderness But my own untamed mind has created a new
My wilderness has made. wilderness now that I know the sun exists.
I think Dickinson is saying that her mind could have handled the same old, same old life as it was (the shade)
until she discovered this blazing ball of light, the sun. Since her mind is naturally wild and untamed (aren't our minds all a bit like that?) she becomes intrigued by the new sight she has discovered. The sun is a wilderness because she is curious about it and wants to explore it. She also may use shade as a metaphor for ignorance, and sun as a metaphor for enlightenment, but I'm only speculating.
I defined wilderness in my first blog post as, ". . . a place untouched or unaltered by civilization. Natural wilderness cannot be staged, as in a park. It isn't without order, but is the ruler of its own order and a form of law that sometimes even holds humanity within it's subjugation . . . Wilderness is also an uncharted journey. It may be a lack of mental stability, or a sense of being lost. It is a great obstacle. It is what we wade through, climb over and come to understand as we find our way home."
I divided wilderness into two categories: the natural world and the human condition. I think Dickinson's idea takes it a step further by making the two aspects mentioned above dependent upon one another.