What is the importance of the play's opening?

That of our lives and ending shows

How transitory we be all day.

l.5-6

This quote, from the Messenger's opening speech is interesting for several reasons: it, right at the start of the play, announces that the play has a moral purpose, and foregrounds the play's dual concerns with our lives as well as our deaths (our "ending"). Moreover, the play's emphasis on transitoriness is expressly stated in the very first speech.