Denny Prokopos was just talking to us about slumps and plateaus. He said he once went four months feeling like his game either didn't improve or got worse.
Sometimes you improve by leaps and bounds, but that may mean you're not challenging yourself enough. Conversely, if you are hitting a wall in training, maybe your training partners are getting better, and if that's the case, then YOU are also getting better, it's just harder to see it because you're not schooling everyone. Steel sharpens steel.