If you rewatch the beginning of season six of Supernatural, it’s painfully evident how hard Soulless!Sam is trying to be the brother Dean remembers. He has no capacity for emotion, no moral compass, but his behaviour in the company of Dean is colossally different to the times when he’s with Samuel. You can see him physically restraining himself, patiently choosing his words, echoing familiar (but dead) mannerisms in effort to reassure Dean that he’s still good-natured well-intentioned little ’Sammy’. But Sam without a soul is unable to feel guilt. He isn’t under any obligation to prove himself to his brother. So what compels him to keep trying?
The Patient - Tool
If there were no rewards to reap
no loving embrace to see me through
this tedious path I’ve chosen here
I certainly would have walked away by now