The Chess Metaphor: The Doctor as the King and River Song as the Queen of the set
"The Wedding of River Song"
"The queen is your only legal move. Except you’ve already moved it 12 times which means there are now 4 million volts running through it."
The Silence has moved River one too many times and she is now sparking and deadly; she refuses to be manipulated any more and cannot be moved by them again. The Doctor is winning the game, but to get what he truly wants— information, both during the chess game and in reality— he must concede the game. He concedes to River, allowing himself to trust her, and marries her, thereby winning his life, information, and her.
Nightmare in Silver/The Name of the Doctor
"You could sacrifice your queen."
While the game in TWoRS has the Doctor facing an outside enemy, the game in “Nightmare in Silver” is his battle against himself. This sacrifice gives up the queen, the most powerful piece in the set, for some positional benefit. The Doctor sacrifices the queen during the game to win in general, and saves the children and Clara. However, in doing so he had to face a darker, more painful part of himself. In the next episode, he faces his tomb, an internal attack on himself, but cannot bring himself to rescue Clara until he lets go of his wife, who he had been holding on to for years— so he “sacrifices his queen.”