AS...
I am terrified I will disappoint myself.
In what way are you afraid to disappoint yourself? Or are you afraid to disappoint God?
If it is God... I think it might help to acknowlege that it's already too late. What I mean is... God already knows every disappointment before you will ever experience it. He sees the whole future and past. He saw it all before time started from our perspective. And yet, it never changed His love. We discover who we are as we go along... but it has always been known to God. So disappointing yourself is inevitable, but God is not 'disappointed'.
When you think about this, you realize that God's love is very safe and secure after all. You can't surprise Him, only yourself. And this can be a comfort to you at the times you fail. God loves you now, even as He sees whatever real failures you may have ahead.
As for disappointing yourself... I've found that reaching the end of the illusions of my goodness only really helped me in the end. It will hurt your 'self', but not 'you'. Whatever process you are experiencing right now is not deadly to you in the way you might fear. Crucibles remove dross; and then the reflection of the silversmith is seen.
I am not trying to be quippy or trite. I hope you can find something in here to rest in.
(((((HUGS))))
bebu
Edited to add: And I agree with underbeliever. TALKING with someone, hopefully a qualified counselor from your church, can only help you out. You don't have to handle this anxiety alone!