When he hears the door open, Cade begins to get to his feet. Rather than deal with the discomfort of occupying a room with someone who doesn't want him to be there, he generally yields the chapel to anyone who comes in after him. Whether or not they're actually upset by his presence, he is fully convinced that he is not welcome among the generally decent population of Skyhold.

He pauses, however, when he turns to see that it's Mia. It's been a while since they've spoken, and naturally he's never felt compelled to bother her with his problems, despite her proving to be a sympathetic ear. It would be a waste of her time, and possibly his.
"Sorry," he says automatically, not even entirely certain what-- or which offense-- he's apologizing for.