You’re boarding up heaven, and you’re locking the door behind you.
I found this scene so heartwrenching and heartwarming at the same time. Dean is comparing Castiel with E.T., he sees castiel as someone who came to him in his darkest hour, his time of need and helped him out of a seemingly impossible situation. No matter what happened after that, Castiel will always hold that special place in Dean’s heart; to Dean Castiel was the hero he needed, when he needed one most.
Loved this scene.