What does Deja remember her mother telling her about mourning doves in the novel, Towers Falling?

Deja recalls that Ma has told her that mourning doves are not really sad. She also recalls that Ma said the doves fly straight and strong. When she considers giving up her hope of learning more about 9/11, hearing the mourning dove reminds her of that conversation with Ma. She realizes she is not really sad, either. Her situation is better than it has been in a while. She finds comfort in that. When she sees the dove fly away, she decides to symbolically do the same, to pursue the knowledge she needs to make a change in her life. She realizes if she does not fly strong and straight like the mourning dove, her life will never change.