Answer: 
 The lines can best be understood to describe how we struggle for knowledge 
 Explanation: 
 Darkness in this poem could be a metaphor for uncertainty, so if people get hits and bruises on their way to know who's there in the dark, that means that people, in reality, has to pass through a lot of harsh situations in order to get the knowledge not only of what it's beyond their sight but also to learn how to deal with uncertainty.