Sam gave him a little nod in reply, noticing how his knuckles turned white. No matter what, Dean would always worry about him. He'd been taking care of him since he was a baby after their mother...He couldn't continue with the thought. It was too painful. He was too young to remember, but he knew it was his fault they didn't have a normal life. 

If it wasn't for him, their mother would be alive along with their father. They wouldn't be orphans going on hunts. They wouldn't have freed Lucifer by accident, he wouldn't have ended up in the Cage, and he wouldn't be soulless.