#it’s like you can see him falling in love in the third gif
Yeah, the tag’s meant to be funny, but no, seriously, look at Dean fall in love in the third GIF. Because Dean has this tremendous fear of abandonment, right? Everyone he’s ever loved, or allowed himself to get close to, has left him in one way or another. Mom, who abandoned him by dying. Dad, who abandoned him for the Hunt. Sam, who abandoned him for Ruby. The friends, the teachers, the mentors, the girlfriends, maybe the boyfriends too. Everybody. And it eventually got to the point where Dean started taking charge and doing the abandoning first — with Cassie, with Lisa — so that he wouldn’t be the one left behind anymore.
And then in swoops this guy, this angel of the Lord, who saves him from Hell, who saves him from Heaven, who saves him from Fate, who saves him again and again and again, and Cas saves Dean again right here, right at the nick of time — this guy who, Dean now knows, for a fact, wouldn’t leave his side even if Sam said yes and the Apocalypse came to pass and everything that could ever go wrong actually did — this guy who is (at this point in the show) demonstrably the one and only person in Dean’s entire life who will never, ever leave him — and when Dean tries to express his appreciation for that, Cas’s only explanation is, “well, duh, of course I’d be here, of course I’d get you out, of course I’d never leave you behind, because we made each other a promise, because we had an appointment”.