One thing that kind of disappoints me is there's no depressed!Dean Destiel stories. It's all depressed!Castiel. And, I mean, it's okay.
But Dean in the show finds himself so useless. He feels like he disappoints everyone. The two things that really seem to keep him going in the beginning are Sam and the fact that he saves people.
Later seasons, he's just trying to find a way he can die. He doesn't think Sammy needs him. That his best isn't good enough. So he puts himself in suicidal situations hoping that he'll finally he able to die. For good.
But Cas or Sam always save him; or he's always brought back.
And every time Sam gets hurt he blames himself. Because it was his job to take care of him. It would remind him of how disappointed John was when a monster would get to Sammy, or when Sam ran away.
Castiel, yes, he has it hard and is disappointed in himself. But I don't think Cas would ever think of killing or hurting himself. When he gets hurt he believes he deserves it, because he betrayed his brother and sisters. He might be kinda depressed, but not nearly as much he is in fanfics.
And in these fanfics Dean's always this happy go lucky guy. I just find it kind of wrong, I feel like Dean would be more likely depressed than Cas.
Because in addition to all of that, Mary still dies in the AU fanfictions. Dean is still responsible for Sam, and John is always angry.
Castiel nearly always has a loving family, I know that doesn't mean you won't be depressed, but that's the canonical reason why he thinks he deserves the pain.
Anyway... That's the end of the rant. Just kinda wish there were more depressed!Dean fanfics.