I was thinking that I might take a walk down to Hogsmeade, since I've already gotten what I need packed, and I'll be taking my homework...

[The worry he feels isn't entirely fabricated. He is still worried, just... for different reasons. Maybe there had been a change in his mission, but still, he wasn't sure why he had to go, when Snape could have gone instead.]

I know, and thank you for that.