Dean is the constant in Sam’s life, the one who’s always there without fail. It makes sense that Sam is only able to distinguish between reality and illusion in the presence of his biggest support. He knows that Dean is there, Dean has always been there, and Dean is steady, supportive, real- even in the midst of terrifying distortions that can make Sam lose faith in every other part of his life.
“Everybody loses everybody and then one day, boom, your number’s up. But at least you’re making a difference. So enjoy it while it lasts because hunting is the only clarity you’re going to find in this life.”
nothingidputbeforeyou 