I frequently felt frustrated and low in confidence when doing the SAT course. I spent ages working through the course prior to taking the mock, so when I got to the mocks I finally felt I was starting to get more of a grip of the subject.
Are you using a training advisor for the course? If you are then it’s worth doing their mocks. I have in the past done the same mock more than once just for practice. The ICB have two mocks for the SAT exam, but I would suggest going back over the areas where you lost marks and making sure you feel more confident and that you have a better understanding before taking the second mock.
As my tutor said to me, there is no rush to take the exam.
The whole course felt like a long road to me but I got there in the end, so hang in there