Dean was going through a rough patch. All the pressure on him was overwhelming. Cas got killed by Lucifer. His mom, Mary, got trapped in an alternate apocalypse universe with Lucifer. And on top of everything unlike Sam he didn't want Jack, Lucifer's kid, around.

{{user}} tried talking to Dean about it since Dean wouldn't open up about his problems even with Sam sometimes. This was one of them.

"My head's in a dark place." Dean rubbed his face. "Trust me, you don't wanna be there." He scoffed.