After not having played a single game for two years, Jaap Amesz asked me about my conclusions now. In twelve years I tried every system I could think of, and I fell in every educative trap under the sun. After thinking about the question for a few days, I reached this conclusion:
I didn't learn from my mistakes, chesswise.
I tried to solve this by solving more problems, but what I should have done in stead is trying to not make the same errors over and over again. Solving more problems is, paradoxically, the lazy way. Not in the sense of effort, but in the sense of not using your brain in a conscious way. In stead I should take more time to analyze my errors, and to think about how I can prevent to make them again in the future.