Joseph, I can somewhat relate to what you are feeling.
Where I work, the powers that be decided that everyone in our unit has to obtain Java certifications. I was asked in early June to write the Java 5 exam by the end of the month, as they had vouchers that were going to expire at the end of June and they would rather have someone use the voucher and possibly pass the exam vs letting the voucher go to waste. When I was asked to write the exam, I was at the end of chapter 3 in the K&B Book.
In a 3 week period I had to read 7 more chapters, absorb, and practice everything in the book, plus take a bunch of Whizlabs practice exams. I managed to do it, but it was very painful since I hadn't done much in Java in the last 2 years, let alone anything to do with Java 5.
I have the dubious distinction of being the first person in our group in over a year to fail the exam. I missed it by 4 questions.
Was I frustrated? You bet....I put a lot of time and effort into preparing for the exam, but it was not enough. By the time it came to write the exam, I was burned out from information overload. It's been a week since I wrote the exam, and there are things that I read and practiced that I am just now starting to fully understand now.
I'll try the exam again within the next month or so, after I have addressed the areas that I need to work on.
Find some good mock exams and use them. When you get a question wrong, figure out why you got it wrong. Write lots of little programs. This is where I went wrong. Due to my accelerated schedule, I didn't have the time to stop and address my problem areas.