To improve, one must sometimes must be willing to endure long periods of "deprovements".
We often think of the path to expertise can be conquered by perseverance and hard work. Perhaps working smart can help a great deal.
This paradigm of thinking is prevalent in almost every sports and shounen anime out there. Keep on pushing and never give up - you will improve bit by bit and eventually hit there.
Haikyuu goes against this popular and often untrue opinion.
[Mild spoilers below.]
In the show, when the dynamic duo realized that their insane quick has hit a wall, they deconstructed their technique and went through a period of hellish training in order to evolve their quick. This meant that they have to endure a massive performance drop against their opponents. Previously they had only lost 2 or 3 points, but when they were in the midst of training, they had to endure losses of 10 or more points, because they kept failing at executing their new quick.
Eventually, when everything came together, it resulted in revolutionary growth that would otherwise not happened if the duo chose to remain in their comfort zone and simply kept practicing their old technique.
This phenomena is evident in elite running (see 80/20 Running: Run Stronger and Race Faster By Training Slower by Matt Fitzgerald). In order to become faster, elite runners train by performing 80% of their runs at a slow speed (below ventilatory threshold). This runs counter-intuitive to the idea that in order to run fast, one has to practice running fast during training sessions. Yes, to run fast, one must not succumb to the temptation of showing off high speeds during training. Short term pride is not worth the last laugh one will get by staying disciplined and being willing to "deprove" to improve.
[Weaknesses]
One of the weaknesses of the show is perhaps the non-realism of the new quick (see 0207xander's review). Maybe the author, or his editor felt that they could make increase the "cool-factor" by giving the ball some crazy spin, but it would have been better if the basis of the new quick is based on principles that are actually applicable to real life volleyball.
As I prefer more-realistic sports anime (the feeling of realizing something cool is actually realistic upon further research is truly exhilarating), this is the one area that Haikyuu falls short of my expectations (thus a 9). Otherwise, this show is a masterpiece.
