Cas's eyes flickered over toward Sam, and when it got too difficult to listen he watched the window instead. Took another hit. Held his breath, exhaled slowly. Sam was getting to the heart of things in a way that no one really had. Dean had been the one to introduce him to drugs in the first place, as an alternative to alcohol, and then just sort of turned away when casual occasional use became worse. They all had to cope with the pain and loss somehow, and Cas chose drugs. He'd say they opened his mind, made him feel bigger, made him feel like he could see more of the universe instead of being so closed off.
But the real truth was, he didn't want to feel the pain.
"The real me?" Cas chuckled softly and it was a low rumble in his chest. "Sam, I'm not the real me."