Honestly --- someone asks him something innocent like 'Well, what's your favorite color' and he freezes because he just doesn't know: he's never felt safe and comfortable enough to stop and wonder such idle things about himself --- it was always survival mode and throwing himself around as a weapon for almost ten years straight.
Sometimes when I'm making myself sad I like to think about the fact that for the entirety of part one Naruto and over half of Shippuden, the only Sasuke that we know is a Sasuke that has been manipulated by someone to do what they want him to do / be a weapon on their behalf.