The very end of "we grow accustomed to the dark" might best be described as

The poem which is the 'we grow accustomed to the dark' in the end, is trying to tell us that even in darkness in which it could represent the darkest days in our life or depressing days that happens to our lives, we could still manage to get through it as life goes on for us and there is always tomorrow which represents the last line as it says that 'in life, steps almost straight'.