To Clear My Head
Disclaimer: I don't own Supernatural. Yet.
Violence -- the crack of a gun, the smack of fists -- cleared Dean's head. Adrenaline made him efficient—at problem solving, or incapacitation, or how to deal the death blow, if needed. Violence was part of who Dean was now, and he went to it like the embrace of a lover.
Hurting someone or something fuzzed Sam's mind. The clarity that Dean sought was his almost all the time now, except when he was inflicting pain on someone else. His mind ticked away regardless of whatever was going on, thinking, planning, and of course telling Sam how he was to blame for everything and, oh, by the way, any time now he was going to snap and kill Dean, and then he was going to join with demons and become evil, and then he'd wade in blood and like it.
Sam loved it when the fuzzing shut off the droning machine that lived in his head. He loved the fuzzing. Craved it, sometimes. It scared him so badly he always kicked those urges to the back of his skull. Hide it, shove it down under mental furniture, bury it.
He'd walk five miles out of his way to avoid a fight with a human being, no matter how steeped in evil, because they were people dammit, people with immortal souls, and as long as Sam respected that line he couldn't be too bad. Too bad, the way people who liked violence could become. The way Sam was scared to death that he was already.