the difference between dean and sam is that while they both create false narratives about who they are and what role they play (in their family/the apocalypse/the grand story etc etc), dean is the only one out of the two who is aware that a role is being played. sam also says things about himself and his story that don't match up with what we see play out on screen, but he's fully in denial of it being a narrative that he's constructed and not reality. the audience might have fallen for the facade dean has painstakingly crafted to protect himself, but sam has fallen for his own facade. which makes good tv actually

like. hubris is his fatal flaw. he assigns so many external factors (the demon blood, how he was raised, etc) to why he makes the choices that he does, but it's all hubris. his entire s1-s5 arc is about his hubris getting the best of him. even when he lets lucifer possess him, he falls victim to his own hubris bc he isn't strong enough to break free (his connection to dean specifically is which is the only reason why they win). and he dies having not learned his lesson which is why it just keeps repeating over and over again ad nauseam in later seasons bc it's a flaw that the writers were either uninterested in exploring in any kind of compelling manner or they just kinda forgot that it was a flaw