Study methods to improve concentration and retention.

Please redirect this post to the appropriate category if necessary.

BACKGROUND:
I have been "studying" for the GMAT for close to 1.5 years without any intensity over a restricted period of time characterized by structure and time management. I have all of the resources necessary to do well: Manhattan Strategy Guides along with a Manhattan course I took, EmpowerGMAT content, and GMATPill access. My main issue is that whenever I have a steady run I eventually reach a point at which I become so confused and enraged that the entirety of the exam seems overwhelming because I cannot see where the studying is leading and how the parts fit together. I lack the principle necessity to employ deductive reasoning in order to break down concepts and focus specifically on such details rather than the larger picture.

METHODS THAT HAVE NOT WORKED:
OG
Completing OG problems under a timed setting, coming back to complete the problems under an untimed setting, and then looking at the solutions. I also tend to get far, far, too ambitious when completing OG problems, retarding my progress completely (focusing on volume rather than understanding).

Manhattan Diagnostic Tests
This was insightful because it clearly shows where weaknesses are (Quant: FDPR, Algebra, Number Properties). Yet no results are found which is a completely accurate reflection of what is happening within my mind—I am not learning a single thing. I have not digested ANY of the content whatsoever, yet have spent way too much time going through material and completing problems in a dead sober state of confused intoxication.

GMAT as a chore v. a hobby
From my perspective, those that do we have (what appears to be) a genuine interest in the exam. How does one become so engrossed in the subject? When someone says they studied "hardcore" for 6 months, what does that mean? Does it mean that you were highly concentrated for three, two-hour sessions, every single day locked in that you were in your own world? How do you reach that level of concentration? Is it a product of a significant number of obligations outside the GMAT leading you to the conclusion that the limited time you have to study needs to be absolutely maximized for retention? Are there specific hours of the day (perhaps the 5pm-9pm) that can benefit from additional structure? I can easily see how having a set routine would make it easier to overcome tendencies to procrastinate, if they exist, and begin to look forward to the time allocated for studying.

CONCLUSION:
If there is one issue it is retention. I like the article by Rich (EmpowerGMAT) stating that the most important skill to master is the skill of learning new skills yet I still have little/no clue how to break into that depth in which I am honestly mastering a new “skill.” It's the deeper lever of concept retention and concentration that I am missing entirely. My current study methods: (1) do not “lock in” my concentration; (2) are often unorganized and unstructured which makes the review process almost laughable; and (3)--with respect to the review process--I am nearly spending the exact same amount of time re-learning the same content rather than ingraining it further.

Any thoughts/contributions are more than welcome.

Regards.