Its like Gaara discovered, love makes us strong, not pain. Sasuke will discover this too. Perhaps Kakashi will show up and give Sasuke a clue about the truth behind the mangekyo(sp?). Maybe he will tell him that the real secret is not killing your best friend, but the realization of just how much that person meant to you. Afterall, sometimes you don't know what you've got til its gone, right? Love is the answer!