She makes it sound very simple.

Well, Castiel already feels the need to look over his shoulder. Though he's not sure what he'll do when he thinks he sees a threat there.

And after what has transpired in the last couple of days, he won't be able to help mulling over his orders.

As for the rest...

"I meant what I said to Uriel, you know," he said.

"I serve God. I always will. I can't walk away. I need to fight for what matters to Him."