You captured the underlying current of their situation perfectly.  I don't think Sam did what he did just because he thought it was right or because he wanted to out-do Dean.  I think he wanted to make his brother proud of him and see him as a man.

Author's Response:

Yes, exactly. I think Sam's biggest goal in season 4 is to have his brother respect and admire him, see him as a capable adult. Thats sadly what blinds him to Dean's warnings. So he messes up, and Dean thinks he's a kid, and he messes up agan trying to prove himself. Its a vicious cycle.

Thanks for the reviews!

Beautiful!  I love everything about it--- the way Sam tells Dean and his dad by just holding out the letter.  I love when Dean sits on the old couch and it slumps beneath his weight and the weight of the world on his soldiering shoulders!  I love when Sam is out of the house and comments that normal doesn't feel so spectacular on that side of the door, and when he hears someone crying and realizes its him.