These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
Lesson one: Do as your mother says no matter what, or horrible things will happen to you.
Lesson two: Revenge will ruin your life.
Lesson three: The strong survive, the weak die.
Lesson four: Do not break away from the group you were born in, or you will be left with nothing.
Lesson five: You should accept fate, and not even try to make your own destiny.
Lesson six: Do not pretend to be something you are not.
Lesson seven: Do not go against your nature.
Lesson eight: Life is not fair.
Lesson nine: It is better to stay in the known than it is to venture into the unknown.
Lesson ten: No Good Deed Goes Unpunished. An important detail to understand is that this story is the product of Japanese culture. One aspect of Japanese culture is that the group is better than the individual. Chirin tried to be an individual rather than be part of the group of sheep, and the film demonstrates the problems of doing that.
Misaimed Fandom: Believe it or not, some viewers believe that Chirin was stupid at the end and that he should have killed those sheep. Some also think that at the end, he should have taken in a wolf cub or a lamb (who should have snuck out of the farm) as an apprentice. Granted, the sheep were not very sympathetic. In fact, all this could qualify as Rooting for the Empire. Depends on the viewer.
Some interpret the story like this: the sheep on the farm represent society in general, Chirin represents the pain and suffering that comes from being a non-conformist, Wolf represents the ultimate non-conformist and the story illustrates the need to conform to society.
Here is another interpretation: the sheep on the farm represent society in general, Wolf represents war in general, Chirin's mother represents the innocent bystanders killed senselessly in war, and Chirin represents the war victims who become warriors and soldiers in an attempt to fight back and to end war violently. By that interpretation, Chirin becomes a warrior perpetuating the war he intended to end, and when he finally ends it, it is too late. He cannot reintegrate back into society and he is left with nothing to live for. The story would then be about the horrors and tragedies of war. One detail that supports this interpretation is that Wolf's name in Japanese can be spelled out as War in English.
Yet another interpretation is that the sheep are all a derogatory symbol of people in general, who are too cowardly to stand up to a threat but consider the one person who does stand up to said threat as a threat to their egos. His courage didn't come at a cost; he had little left to lose in the first place, considering how all the other sheep treated him by their apathy for his loss. In other words, to show a major thing wrong with society.
‹bermensch: Wolf is most certainly this. The Last Man turns out to be the whole flock of sheep. Chirin starts out as part of the Last Man, and he tries to follow Wolf's example to become the Ubermensch. He fails. Why? Wolf is the Ubermensch because it is his nature. Chirin tried to become one for the sole purpose of killing Wolf to avenge his mother's death. The problem with that is that the Ubermensch is not supposed to be driven by revenge or emotions attached to such concepts. Another problem that causes Chirin to fail is that it is in his and his kind's nature to form attachments. He proves to be unable to kill off the Last Man when Wolf tests him to do so. He ends up killing off Wolf because his attachment to his past and his mother is stronger than his attachment to Wolf. The Last Man rejects Chirin, which leaves him with no one to become attached to. In the end, Chirin realizes that he failed to become a wolf (i.e. the Ubermensch). Chirin failed to realize that the Ubermensch has to avoid being dominated by attachments. He also failed to realize that he had to think about what to do after he achieved his revenge on Wolf. Chirin failed to realize that the Ubermensch has to be a leader with a vision and not a follower. He failed to build up any society and dies and becomes a ghost as a result. This story seems to demonstrate what can happen when the Last Man tries to become the Ubermensch.