so here’s the thing about Dean Winchester
he cares about everybody, except himself. He’s willing to CUT HIMSELF WITH A MANCHETE to get a vamp, when he gets hurt it’s really not treated like that big of a deal. This season he spent a good deal of time running on a still-healing fracture. He drinks to the point that Sam made a joke that it was impossible for him to get drunk now. His life is full of self-destructive behaviors, but only to himself.
I think that Sam sees a lot of John in Dean, that’s why he doesn’t stop Dean when it gets too bad. That’s why Dean is continuing on and on to kill himself slowly (the only thing he hasn’t taken up is smoking, but you can’t hunt like you should when you’re hacking up your lungs. Becoming an alcoholic is much more suitable for hunters) and nothing is stopping him.
But the saddest part of all of that, is that he doesn’t really want to go slowly. He wants to die in a blaze of glory, a hero’s true death. He doesn’t want a hunter’s funeral, he wants there to be nothing left to burn.