You sit looking out the window as your train pulls into the station. Some on the platform stand there waiting to board and some stand there waiting to say goodbye wishing it was their train and that they were coming along.
As your train sits in the station another pulls in. You watch the platform people look up at the new arrival and like them find yourself gazing at the other train wishing you were on board. Glancing across the platform you see someone on the other train looking at you. You nod at each other knowing that you both understand.