Try to look for patterns in the types of questions you are missing. For example, are the questions you are missing in thermodynamics, molecular bio, VR extrapolation, etc? Once you have categorized what type of questions you are missing, try to see why you missed them. Was it a careless error (not reading question correctly or forgetting to include something simple) or was it because you genuinely don't understand the material. If it's the former, make a note of it so that you'll be more careful next time. If it's the latter, review the material before taking another practice exam. Hope that helps some.