"I do understand," Castiel murmured. He could imagine the pain of losing his faith, had come close to it during his time as a mortal even if he had never crossed that line into loosing it completely. "I suppose the faith is different when it is your own family." It would be like Dean losing faith in John.
He swallowed hard, looking down for a moment. It made him feel weak to admit to having the darker emotions, jealousy, anger. But he couldn't deny the power they have over his life, just as much as love and faith.
"I won't ask you to walk away forever, though sometimes I will ask you to walk away for a time," he warned her. "Even if Sam himself doesn't ask you to stop, if I think you're pushing too hard, I will ask you to. He may never understand and you can't force him to. And his priority needs to be elsewhere." He looked away with a half shrug. "As does yours."