Almost done with season one. Can you believe it?
All he ever wanted was his brother. As long as the demon stayed alive, Sam would stay to hunt it.

He blocked his brother's way into the burning building, citing suicide as his reasoning. He knew in heart that that was a lie, though. Sam had the Colt, and with it, he could kill the demon. If Sam killed the demon, he would head back to Stanford. He'd said so himself.

So Dean pulled him away from the fire, breathing a sigh of relief as the demon faded into the flames and Sammy stopped fighting him. His brother was going to stay with him. It was because of this that he knew he was selfish.