BALONEY! - is what I have to say to the prior replies to your initial inquiry.
My coach Thomas Mark, who some consider to be the best technique coach in the world, teaches his students that if what you are working on does not improve in a couple of "days" then you are not playing it properly.
And, if you are not playing it properly, you are either deaf, or more likely your teacher is not teaching you the proper manner in which to learn/practice a piece.
The big secret in piano pedagogy is that most piano teachers are not qualifed to teach someone how to pump gas. They not only do not know how they do what they do, they also do not know how to teach anyone else how to do it.
I suggest you get copies of the Taubman tapes from your library, and then study them diligently. Then, get a copy of Thomas Mark's book (from the library) which is entitled "What Every Pianist Needs To Know About The Body."
Next, go online and find out where the nearest Dalcroze Eurhythmics teacher is, and then sign up for a class. I strongly suspect that you have significant rhythm problems, also.
After you have done all this, you willl have realized that playing the piano is not the rocket science that the world makes it out to be. It is basic natural body hand eye choreography that can be taught to anyone.
Finally, get yourself a teacher who has heard of these three prior sources - Taubman, Mark, and Dalcroze. Then, you will discover the true joy that is playing the piano.
Good luck to you, and remember most of all, it is not your fault!