The Doctor: "I am really stupid. And I'm growing old..."

It's the way he says that last line that got to me. It's not said in a 'Oh bother, I'm forgetting things!' way. No, there is a definite sense of 'It's all downhill from here' - that one day he'll be unable to run any more. Only two regenerations left, and then he's done, and I think he feels it keenly.

Any thoughts? I'm half asleep and going to bed now...