[It takes a long time, at least relatively speaking, for the boy to realize that she was talking to him, because in truth, she's the first living thing he's ever met that can talk without being human. Of course, even that fact isn't too far out of the realm of weird he's been living in; unfortunately, even her grace and charm can't completely counter the fact that he is actually rather frightened by large animals - even ones as regal as Celestia.

His hands, clenched in fists at his side, don't move, and it takes an effort of will for him to force a slow breath, closing his eyes for a moment.]

I wasn't...um. Looking.

[His voice is much weaker than when he first apologized, and there may even be a quaver to it, but he presses on.]

I should have noticed that you had stopped. Really, sorry.

[Situational awareness keeps one alive. Running into someone because he was distracted is a good way to get himself killed...at least, it was back home. Here, he's still going to act as though that's true, because the last time he lost focus, a bunch of evil spirits almost ate him.]