semirahrose:

In seasons one though (most of) season 5, Dean, out of fear (and probably an ingrained tendency to expect the worst case scenario), could not cling to faith that Sam was not evil and could make choices that would affect his own destiny. 

Sam was not, in fact, evil, and always had the ability to take his own fate his his hands and the love for and faith in people that has made him such an amazing character. But there wasn’t another Sam to mediate for him, so the brothers had to struggle for each bit of insight.

It’s so heartbreaking and hopeful and lovely to see Sam tentatively stepping in with hope for another person with an evil birthright, and it’s humbling to see how things could have been—would have been—if things had been different.

I’ve said this a million times, but… if Sam had a Sam to fight for him, things would have been so much different.