I'm worried I might not perform well in the exam

Guys who have tried PLABABLE,
I’m worried I might not perform well in the exam. I’m solely studying from plabable and I plan to go through Mocks afterwards.
I get a score of around 66-70 % in the first time to clear a category. I haven’t finished 1st review of the questions yet and will try to go through them for a second time, but I think I have already forgotten what I have studied.
So.my question: Is it normal to feel this way?