Jensen Ackles previews Supernatural season 10 (x)
I think that for Dean, realizing that Sam wouldn’t just ‘let him go’, is to see that Sam really loves him and cares for him, especially after the last thing he told Sam, ’I’m proud of us’ that by them he really let Sam go, now, seeing Sam choosing to look for him, to help him, realizing Sam is doing this out of love and not out of duty, something will change.
I think, one of the most challenging things for Dean will be to let Sam help him. Dean never let anyone help him, not really. And this is a huge opportunity of growth for Dean, and for the boys’ relationship to grow as well.