On the year anniversary of Castiel's death, Same found Dean with slit wrists and an empty bottle of whiskey beside him. All that was written on the suicide note was,
'Keep going, Sam. Keep fighting the demons. Don't give up. Don't try and save me. Let me go and move on. I am so fucking sorry but I can't hold on anymore. Keep going.'
There was a small section scratched out where Sam could make out the words, 'Cas', 'love', and 'fuck'.
Staring at Dean's body, still bleeding onto the tile, broke Sam. He left Kansas for the last time and didn't look back. He kept going, went ruthless and did nothing but kill. Sam had nothing left, and let himself become someone he didn't even know, someone Dean would never recognize.