‘Another clue is in how protective Sam is of Dean’s feelings in this episode, even though he’s literally losing his mind. Sam’s so protective, in fact, that he held off on telling Dean about his hallucinations because, “you got a lot of pretty severe crap swinging your way lately, and I thought why burst the one good bubble you had left?”
And yet… what “severe crap” has Dean had going on? Team Free Will doesn’t really have anything to do, no monsters to chase or problems to fix. Cas is all over the globe, Eve’s gone, demons are mostly quiet, and so Dean’s not really doing much of anything. For most of the episode all he’s done is fix the Impala, and mope about Cas.
So it’s not as if by “severe crap”, Sam’s referring to some great time-suck of a hunt that they’ve all been on. He is explicitly referring to Dean’s anguish over Cas, which Sam calls “severe crap”. And that means something big, because Sam is the king of acknowledging feelings that Dean won’t admit to anyone else, even himself (I mean, half of Season 3 was about how Sam had to drag Dean’s fear about going to Hell out of him, remember?) So when Sam acknowledges Dean’s dealing with “severe crap” in losing Cas, he knows what he’s talking about.’