The problem with being around each other constantly was that even the tiniest of problems got blown up into a massive issue - then factor in all the other crap their lives threw their way and it was really a wonder that they hadn't murdered each other by now.
Sam could be laid on a big comfy bed right now with a gorgeous woman at his side and a cute dog at his feet. But no, he was sat on a cramped sofa in a damp cabin with Dean. But Dean was right. Sam had chosen this path. He had chosen his brother over happiness.
He could still change the subject and avoid the growing mountain of problems. Dean had given him the chance to back out of talking about it. But instead he shrugged. "We better do a beer run before we start."