In addition to what Piltdown Man and Matt101 have posted, I'd add that you should consider that everyone finds some of the subjects easier and some harder. Normally Met and Gen Nav are the two people find hardest, but you might find they just "fit" the way your brain works. Finding something you CAN do, and diverting attention there for a couple of hours is a good way of fending off the frustrations of not understanding Lamberts conical conformal orthomorphic charts at first glance
The other thing to consider is that to succeed kind of takes what boxers call "heart" - there will be many, many, many times you'll want to put your CRP5 through the wall, but if you have the perseverance and will power and determination and sheer chutzpah to carry on, you'll get there eventually. Just be warned that the mountain of rice (PM - nice analogy btw!) doesn't go down very quickly and can seem very daunting even just before the very last teaspoon full.