Getting out of IP can be scary for alot of people, so it's understandable you feel this way. IP can become a bit of a safe place for many people so the thought of facing the world again can be a scary thing. However IP long term isn't always the best thing as it doesn't allow you to develop your own coping mechanisms instead of relying on just other people to keep you safe.
If your psychiatrist thinks your ready then you probably are, I think part of you knows too but at the same time it scares you. It's okay to be scared though. You might relapse, but you know what you also might not. The choices are in your hands, you can choose to eat or not eat. I encourage you to give it a go though, and don't be afraid to reach out for help if you need it. All the best