He had never imagined a day when the door of the house would be closed to him. The last time he had seen his mother, she had called him a monster and prayed at him that he would go away.
-- Narrator (Prologue paragraph 3)

Importance: Simon’s reluctance and unhappiness with being a vampire continues in this novel. Simon feels horrible about being a vampire because he never wanted to be a vampire. He is made to feel even worse because his condition has forced him out of his home and turned his mother against him. Only Isabelle manages to help Simon see he isn’t a monster as the novel progresses.

Both of you,’ said Simon, ‘blame yourselves for things that aren’t your fault.
-- Simon (Chapter 2 paragraph 133)

Importance: Simon speaks to the issue of Jace and Sebastian where Clary and her mother are concerned. Both of them blame themselves for things that aren’t truly their fault...