For one to know hope, one must know hopelessness first, you say - I think this is a very key point and one that is very true. In fact, both hope and hopelessness walk hand-in-hand; are virtually one. I mean, without hope, hopelessness is simply 'lessness'. The two are both two sides of the same coin. The coin is nothing more than life itself.
I think the most important part of the poem is the first line of the second stanza, the word 'somehow' especially. ' 'Somehow' light of hope arrives. How is it so? It simply is. That is the beauty of life; as soon as we let go, things simply fall into place. It happens 'somehow'.
RE: Explain