First, you start questioning your past. You can't remember exactly where you started getting ill. And you doubt your mental abilities. Clearly, you made a big mistake by not adding two and two together. Your faith in how you understand the world goes.
Nothing seems to be sure anymore.
And don't forget that changed emotional make-up. I had become a different person. Second, you lose the future. Normally you tend to identify with your abilities, the things you like to do, your interests, passions, dislikes, etc. They were all gone.