Her death the dividing mark: Before and After

Okay so I cant quite pinpoint anything about this quote but I KNOW that it is important.

Can someone help me enhance my point below:

Her death is described as the “dividing mark” of “Before and After.” The capitalisation of “Before and After” may imply that the narrator sees his life in two parts ; before his mother dies and after his mother died , this illustrates that her death has affected him a lot and she was a huge part in his life as it has led to him xxxx ( idk what to write here)

Furthermore, this is the first sentence of the paragraph this implies that the writer wants to focus our attention on it and xxxx

A colon is used after the narrator proclaims “her death was the dividing mark : Before and After”
Colon emphasises the fact that his life has been divided into two parts.