Milton's expresses fear that somehow his blindness will keep him from using his talent in God's service, thus separating him from God's favor. This idea is that somehow we need to "earn" favor with God through our service. The poem's blunt reponse to Milton's lament is a reminder that "God doth not need either man's work or his own gifts...who best bear his mild yoke, they serve him best."
In a world that is obessively concerned with performance for gain, Milton's poem is a stark reminder that our job is to "bear the yoke". But what is the yoke? I am currently rereading Dietrich Bonhoffer's classic, The Cost of Discipleship. Bonhoffer makes the case very elegantly that our our response to call of Christ's saving grace is not "to do", but rather to "follow"... wherever he calls us to go. Bonhoffer's discipleship cost him his life. He was hung by the Nazi's in a Third Reich prison. The cost of true discipleship is summed in lines of the classic hymn, "Where he leads me, I will follow".
" God loves...God calls... therefore I serve." I wish I could honestly say that describes me. It doesn't, but I want it to. :-)