This story was inspired by the episodes up until Naruto Shippuden episode 52. I'm not a big fan of this story, now that the anime has gotten much further than it was when I wrote this. It made a lot more sense back then, but I figured I would still post it just to get it off my mind.
Disclaimer: none of this belongs to me
Sasuke knows that on the outside, he appears apathetic and hateful to Sakura and Naruto. But when he stops lying to himself, he knows that deep down, he only does it because he cares so much. And that scares him. Because the last person he cared for hurt him deeply. Those scars still have not healed and Sasuke doubts that they ever will. His single goal now is to avenge his family, by destroying his older brother. But Itachi is so much stronger than Sasuke. And Sasuke is afraid that he will not be able to gain enough power fast enough.
He knows that some day, Itachi could return, and again destroy everything and everyone that matters. Sasuke cannot bear to lose Naruto to his brother, or watch Sakura be twisted and tormented by the Mangekyo Sharingan. And so Sasuke has to become stronger than Itachi, as fast as possible, so that he can keep his friends from harm. Until then he lives in constant fear of what could happen.
When Sasuke finds Itachi and Kisame trying to take Naruto from the room where the boy is staying with Jiraiya, he is terrified that his worst nightmare has come true. Itachi has come after one of the people that Sasuke cares about. He has no idea what his brother and the Akatsuki want with Naruto but it doesn't matter because Sasuke won't let them take him anyway.
But Sasuke cannot protect Naruto. Jiraiya is the one who steps in and saves the day, driving away Itachi and Kisame while keeping Naruto safe from the Akatsuki. And now that Jiraiya knows that the Akatsuki are after Naruto, he will be carefully watched over. Naruto is much safer than Sasuke could ever make him.
So Sasuke decides to leave, knowing that Orocchimaru can give him the power that he desperately needs. Naruto and Sakura will be fine in his absence, carefully watched over by Jiraiya and Tsunade. It is time for Sasuke to learn how to defeat Itachi, to learn how to protect Naruto and Sakura. First he has to convince Naruto and Sakura and the others not to follow him, that this is for the best.
But no matter what he does, Sasuke cannot make Naruto and Sakura let go. Sakura tries to hold him back arguing and threatening until Sasuke knocks her out and leaves her on a bench. Naruto and others follow him, destroying the Sound Five, and Naruto almost succeeds in defeating him. But Naruto cannot handle the power of the Kyuubi, and collapses right when he could have succeeded. Sasuke knows how Itachi received his Mangekyo Sharingan. But he cannot bring himself to destroy Naruto in order to earn it as well, because Naruto is the most important person in Sasuke's world, and everything he does is to protect Naruto.
Three years later, when Sasuke, Sakura, and Naruto meet again, all three are widely different from their old selves. Sasuke is glad to see that Sakura and Naruto have also been training and, even though he is still more powerful, they will be formidable opponents for anyone who tries to take them on. And now that Naruto has seen the level to which his power has progresses, he knows that the other boy will drive himself twice as hard to become strong.
When Sasuke tells Sakura and Naruto that he does not care what happens as long as he gets revenge, this is mostly true. Of course, he would much rather be alive, so that he can continue to watch over his friends. If he survives, maybe he will one day be able to reconcile with them. That is what keeps him going, allows him to stay near Orocchimaru, prevents him from going back to Konoha. Now is not the time for Sasuke to become weak. He has already given up so much to keep his friends safe. When he defeats Orocchimaru and Itachi and the Akatsuki, then maybe he can try to rekindle his relationships with the people back in Konoha. But for now, Sasuke will continue to grow more powerful and to watch over his friends from a distance.