My brain says the most damaged people often end up together and either one of two things can happen: they inflict more pain on the other or they find a way to heal each other. Sometimes, it's both of those things meaning the same thing. Derek Morgan and Emily Prentiss have the tools and background for all of this to occur. They fucking love/hate The Job, so maybe they start sleeping together just because it's easy and it's the only way to cope with The Nature of The Job without completely imploding. But then maybe it means more than either are willing to admit. Of course, Emily would freak out and do something drastic like, unintentionally cheat on a non-existent relationship with a non-existent boyfriend in her all to existent Job. Derek would, of course, shut down and out and lick his wounds for a spell before realising that she's just as fucked up as him because he now understands what it is that drives each of them to be Self, baggage and all, in doing. their. Job. And, because I like a happy ending, Derek makes Emily realise this fact too and they make a deal to call a spade a Spade. Not all is forgiven but maybe they can learn to love in the face of The Job. And then there's lots and LOTS of hot make-up sex. Here is a musical representation of that in my brain.