Hi George,
I think there is no problem in the way you studied. Everyone prepares in a way that suit's his style. 6 months was good enough time allocated. Also it seems like you had enough practice test questions.
Please don't be discouraged we fall only to stand higher.
I will suggest you some tips ,may be they will help you.
1) Don't give up and please try hard to in next attempt.Remember you are almost half done by qualifying for exam which is a tedious process.
2)Do not lose your heart or confidence (easier said than done) , it might just have happened because of anxiety on the day of exam trust me.
3)Focus on EVM,network diagram and EMV calculation questions. They are simple and you are not confused on choosing answers.You can get 18-24 answers right here.
4) Focus on ITTO many say you don't need to focus on it but if you get these right you secure 6-8 easy answers.
5) Quality is easy topic focus hard on it make sure you get all answers right here.
6)Scope is very easy again make sure you get everything right here.
7) HR and communications is simple and study the Bruce Tuckman's Ladder and the Conflict resolution techniques well.You can get some easy questions on this.

In risk study the risk strategies well.
9) Remember types of contract and when and where you use them. You can again get some easy questions right here.
I know George you must have done these things my point is when giving PMP exam when you get all these questions right your confidence goes up and chances are you get difficult questions right afterwards.
Important note: If you can't answer some questions or feel discouraged during exam ,tell yourself these are the 25 questions which won't be used for scoring keep yourself motivated throughout the exam.
You know even before scoring if you are going to pass.
Finally AL THE BEST and I am sure next time you pass with flying colors:)
-Sagar,PMP