In Patrick Ness's A Monster Calls, what overall theme is presented through the changing relationship between the monster and Conor, the protagonist? Please provide quote examples.

In Patrick Ness's A Monster Calls, the evolution of the relationship between Conor and the monster reflects the theme of self-awareness. From the outset, the monster serves as a guide and tough-love mentor to Conor, teaching him through experiences that sometimes result in bad behavior (wrecking grandmother's apartment and beating up Harry), but simultaneously imparting wisdom about the 'whats' and 'whys' behind these actions. For example, the monster poses questions during his stories that help Conor understand his own conflicted emotions and desire to hurt others:

Humans are complicated beasts, the monster said. How can a queen be both a good witch and a bad witch? How can a prince be a murderer and a saviour. . . How can invisible men make themselves more lonely by being seen?

By encouraging Conor to be self-reflective, the monster empowers him with tools to come to terms with the hard truths of his life.
Initially, the relationship seems quite adversarial in certain ways because Conor doesn't understand the message in the monster's stories and continues to act out and be sarcastic. As Conor's self-awareness grows, however, the monster's language softens. For example, the monster helps Conor forgive himself for some of his previous destructive attitudes and behaviors, saying, “You were merely wishing for the end of pain. . . Your own pain. An end to how it isolated you. It is the most human wish of all.” The monster wants Conor to be free from denial and to learn to discriminate between lies, constructed reality, and truth. 
By the end of the novel, the relationship has echoes of a parental connection: "He [Conor] faintly felt the huge hands of the monster pick him up, forming a little nest to hold him. He was only vaguely aware of the leaves and branches twisting around him, softening and widening to let him lie back." By releasing his fear of the truth, Conor feels more secure in who he is and recognizes that he is, in fact, loved, symbolized through this final, tender image of protection.