Re: 7X05 The Angels Take Manhattan (Grading/Discussion) (SPOILERS!)
I think Eleven is more mature than some of us are giving him credit for. However, when it comes to people like River, Rory, and Amy, he doesn't see clearly. This is the first time in a very long time that the Doctor has felt like a part of a family, and he understandably doesn't want that to end.
He's also seems to have spent more time with River and the Ponds than any other companion that we know for sure about. He mentioned that he was around 1200 in an episode and he was around 907 when he first met Amy. So a quarter of his entire life as been with them. Also it is probably the best relationship anyone ever had with their in-laws.
Awesome Possum is in the Burn Book