I felt like UWorld helped prepare me well because of the rationales for each answer. Beyond that, UWorld gives you additional context outside of the answers they provide. It also mimics the test format which helped me stay calm during the actual exam.
Make sure you understand WHY you got the questions wrong. Was it: you didn't know the content in the question or an answer, you changed your answer, you misread the question, you didn't understand the question type, you had to guess? etc. Keep a tally on each quiz or assessment you take. Look through all of your wrong answers and determine what category of "why you got it wrong" it fits under. For me, my top two categories were lack of knowledge on specific content and misreading the question. Knowing this, I came up with ways to avoid misreading any questions. Over time, I found that each following assessment I had fewer and fewer wrong questions due to misreading. If it's a content issue... look at your wrong answers, pick out a FEW key/major content areas that you SHOULD have known..now brush up on those topics. Don't overwhelm yourself with trying to know EVERY detail. Cramming won't help.
Also, make yourself a word document and make a list of commonly tested lab values, drugs with narrow therapeutic ranges (ie. digoxin, valproic acid, dilantin), and S/S of both hyper/hypo (Na+, K+, Ca+, and Mg+).
Best of luck, I believe in you!