James Goss said this quote

How are you, Rory?' [the Doctor] asked.I [Rory]... answered him. 'It's been odd being you.''Isn't it?' The Doctor's smile didn't quite reach his eyes.'How do you cope?''Ah...' The Doctor picked away at a scrap of loose paint on the door. 'Well, I just get as close as I can to a happy ending, then I shut the door behind me and move on.'I nodded.We shut the door behind us and moved on.