In the beginning of Thor: The Dark World movie, there's a conversation between Thor & Odin:

Odin: Is Vanaheim secure?
Thor: As are Nornheim and Ria. Though our work would have gone more quickly with you at the fore.
Odin: You must think I'm a piece of bread that needs to be buttered so heavily.
Thor: That was not my intent.

What's the meaning of all this? I am not a kind of philosopher guy, but is that a way of telling that he was old or weak or something to draw lots of black magic to survive wars? Why couldn't Odin go to wars?