You know how it ends. [Spoilers for KHII, second person POV, obligatory Axel-Roxas fic.]
It ends with the seats around you emptying one by one because you're a Nobody and playing idiots stupid enough to think you're on their side is what you do; because Nobodies don't do too well against kids with giant keys - he's kicked all of your asses, and let's face it, if Nobodies were as good as the original you wouldn't all be looking for hearts, would you? - and because if you hadn't stepped in, Marluxia might have had a chance.
It ends with him gone no matter what you do - no matter how many "traitors" you weed out, or how you manage to get Sora out of the way, he's not going to stick around because he's not like the rest of you. His Other's still alive, he's still got a heart somewhere - everything you do's just gonna delay the inevitable.
It ends with you turning on the Organisation - yeah, like that ever worked out - and going after him, it ends with you not being able to save him because he never listens to you, it ends with you down and dying because you're stupid enough to think that the pain inside your chest - and that was his fault, always his fault - was worth everything you have.
You know how it ends.
And you carry on anyway.