Why I have to solve more questions if every time I face a more new questions and concepts?

Why I have to solve more questions if every time I face a more new questions and concepts??? Whenever I do more questions or self assessments I become more frustrated because most of questions are new to me and some of them are not covered in FA or UW…
This is an endless process,
And in the real exam I will find a more new questions and concepts :tired_face::tired_face::tired_face:

How to calm myself when I face questions that I never knew it before because I always get them wrong and in addition to that I become anxious and I start to loose time management and rationale for other easy questions??? Any advise???