THE PROBLEM:
Sadly, there is no way you can consciously process all that is required to play your instrument. It's impossible. Many students get frustrated with how slowly they feel they learn music. Especially adults! They think that it's because they're too old to learn.
THE GOAL:
Think about music progress as an endless list of "tricks" or "tools" for your instrument. There are millions and you can't think about them all. That's why it is the goal of every musician to take whatever concept is directly in front of her and move it back to the subconscious by practicing over and over. We're just trying to stop needing to think about what we're thinking about so we can start thinking about what we're not yet thinking about.
SO WHAT?
Don't attempt things way out of your league. Even if you conquer that piece, it won't do you any good in the long run. You won't actually have the cumulative skills required to play pieces like it, you'll just have memorized that one song.
In fact, it may be helpful to make an actual physical list of the things you've learned. The fact that there is always an ocean of tools out beyond our grasp is humbling, and sometimes de-motivating. Keeping track of what you're working on gives you an important list to see how far you've come. All Milestones Music students get this updated list each week, so students can track their progress for encouragement and motivation.