What is the importance of writing, namely letters and poems, in the book, The Things We Keep: A Novel?

In the novel, writing serves to symbolize the act of remembering and facing hard truths. Clementine writes a poem about her father, trying to remember what he was like and what he used to play with her. She also solidifies the point, and remembers, that her dad is heaven and not coming back. Anna writes a letter to herself about a promise she makes to Luke that she will stay with him and not kill herself. Both characters are faced with an ugly truth, but are still looking to remember the good parts of it.