Momentariness, but birth and death?
I would say there were two ways of looking at this.

You can't exist &quot;for&quot; an instant but you can exist &quot;at&quot; this instant.
You are not living five minutes ago, or two hours in the future.
You are living at this precise moment.
&quot;You&quot; are living in this instant and this &quot;you&quot;
is different to the &quot;you&quot; of last week or last year or five mins ago.  As you experience things, you change and become a different person.  You don't die or become a different being.