"I daresay no one does," Severus answered with a shake of his head. "That's probably what they're actually testing -- how long before we all go 'round the bend." He shrugged slightly and added, "But you don't have to be sorry. You're allowed to get tetchy every now and again." He gave her a sidelong glance, with a wry smile, and added, "Just don't make a habit of it. That was my mistake."
He thought for a moment of giving her some pointers of how exactly he'd managed to cope living that way for so long, but he decided against it. Because he really didn't have any pointers to give, apart from staying on his own and having as little contact with anyone as he could. That probably wasn't what she needed to hear right now, anyway. That really would turn her into him -- again, apart from the fact that she was pleasant to look at -- and he really didn't want that at all.