Finn and Poe are together and happy, Poe even decides that considering what they do, they could die any day and asks Finn to marry him. Everyone on base is happy for them and Luke even offers to walk Finn down the aisle. Poe's father even comes and Leia even manages to get Finn some original Naboo wedding robes and everything.

The eve before this is all meant to go down...Finn breaks up the arrangement. Poe is heartbroken, everyone is confused and even the other pilots are ready to shake Finn down for an explanation. And Finn refuses to explain himself, even to Rey.

The fact is that Finn had been reading about the old stories, finding out about Anakin and Padme and begins worrying that something similar could happen to him if he becomes too attached to Poe. After everything he's done to distance himself from the First Order, he's terrified he'll fuck up and end up tempted by the Dark Side anyway.

Happy or sad ending up to author.