"No, Meg, that's not what I was saying," Castiel began to stammer out, realizing the shift in her mood, her sudden anger at him. He hadn't meant for what he said to her to come out like that, because it wasn't the case at all. And, had he more knowledge on how to speak to women, on the things he should and should not say, he probably would have known never to say something like that to a woman. Especially one that he was in love with. And one who happened to also be a demon, at that.
So, he pushed off the wall of the elevator when they reached his floor and took quick strides to catch up to her. He darted in front of her, to stop her from getting to his door before he did, because he wanted to explain to her before she entered his home. If she got past the threshold and was still angry with him (not realizing of course, that she was still hurt about his words, only picking up on the anger of the moment) he couldn't be guaranteed that she would stay.
"I don't want you here because I need you, Meg. If you're going to be here, with me, I want that to be your choice. Free Will is a beautiful thing." A beat, as he thought more about what he was saying, about what she'd said, before. "If you're here only because I need you, require you to be my care taker, once I no longer need you for that, you would have no reason to be here."