An amazing trip

One day, while I was walking my dog I saw a little boy far away. It seemed that he was going to the train station. When I checked he got inside  I tried to follow him crossing among people. He went to the ticket window so I approached enough to hear what his destination was:



-Ticket clerk: " Okay, here is your ticket but before you must know something"

-Little boy: " Of course, tell me."

- Ticket clerk: " This is only one-way ticket, that means you know when it begins but you don't know when it finishes...

 I left the train station and on the way  home I was thinking a lot about that conversation.
Finally, I understood all, I already knew what the boy's destination was:

the life.