So many people enter and leave your life. Hundred of thousands of people. You have to keep the door open so they can come in. But it also means you have to let them go. 

Paris departing 

Milan arriving 

Everyone was coming or going

People around the world were moving from one place to another. 

No one was staying.

I said, What if we stay?

--Jonathan Safran Foer, Extremely Loud and Incredibly Close