What does the speaker realize by the end of “because i could not stop for death”?

By the end of the poem “because I could not stop for death”, the speaker realises that all the centuries which have been passed feels shorter than the day. The day in which she imagines of nearing to death, that day is much longer than her entire life. She took the fateful ride through carriage and that felt to her as the longest journey. The time which she spent gave her the idea and the truest meaning of immortality.

the present continuous is a verb tense which is mainly used to indicates that an action is in progress at the moment of speaking.  

it is formed using: person + verb to be (am/is/are) +verb + - ing form  

example: i am studying at this moment .

in addition, the present continuous is also used in order to express things that will or will not happen in the near future.

example: i am having dinner with some friends tonight.

the speaker sometimes   uses it   to express that an action is repeated and it causes irritation on the part of the speaker

example: my sister is constantly complaining about everything.

they fear for their lives