It is important to know your (not only mathematical) limits – when you know what you can do and what you can’t do (yet), you know where you need to focus your efforts to improve your skills. This applies to everything in life, not just mathematics.
Have you spent time analysing your own skills in mathematics? Have you looked at the list of skills that you are expect to have (and be able to demonstrate in a test) as you complete each section of study? If you haven’t you can (and should!) read the study design document at this link.