It is very common to hit training plateaus in ALL endeavors and slogging through them is the mark of real committment.
I've heard it said that during these long plateaus there actually IS active learning going on, it just isn't integrating/manifesting yet and that eventually there is a real Aha! or shift that occurs.
A very common experience for me is to go to a seminar, feel completely frustrated and underwhelmed by it, and then get back to my regular practice and realize that I've taken a big jump. Sometimes you need a different perspective in order to improve.