THERE ARE TWO WAYS SEASON 8 SAM CAN HANDLE LOSING DEAN
Version 1 Sammy has it together, at least enough to move forward, has a plan and is ready to go! He’s got his trusty sidekicks - hopefully people like Garth, Jodie, (Frank? Rufus? I think they’re dead?) and a lifetime of experience on his side to help find Purgatory. Perfectly capable of handling a few side missions like he and Dean did back in the day, plenty of potential for character development and no matter what there’ll be brother angst, and also a successful driver of the plot.
Version 2 Sammy is familiar, we’ve seen him in Mystery Spot and something similar in Soulless!Sam. When he lost Dean he decided nothing mattered more than finding him, and so he shut everyone and everything out, maintaining his own well-being only enough to continue hunting. He doesn’t care, nothing matters - nothing but his goal. He’s cold. He’s empty. Version 2 Sammy is more of a plot device than a main character, and we’ve already explored this particular angst. Sam has changed since Mystery Spot and now is an excellent time to see exactly how.