It's up to Dean to feel happy for someone else or not, nonnie. He has a right to his feelings. And if he believes it's possible for Sam, he'll be happy for him. If he doesn't, he'll always look on Sam's normalcy with concern for him.

Any loved one feels happiness or concern when they believe their loved one is making a good choice or not. It doesn't mean they interfere and keep them from making the choice... it just means they're happy for them or worried about them.