This is just so revealing about how the Doctor feels about himself. Just with the last sentence, we can see he thinks that he is dangerous. He brings harm to people. Amy is trapped in Demon’s Run, her child is a prisioner of the Silence and, in the end, it will be all because of him. Because the Silence fear him. So, he has to have lots of rules, because he is not a good man. He killed his own kind, and brought so many suffering to so many friends that he doesn’t have other choice but create lots of rules. It’s a sentence that shows how powerful the Doctor is, but also, underneath, how this power is slowly bringing pain to his friends. For him, it’s all his fault.