Its very simple, lots of manga & anime teach you different things and its up to you to take from it what you will.
What I've learned Hitman Reborn - Take pride in your friends. Yu Yu Hakusho - If you don't know what your fighting for, them fight to protect your friends. No matter how strong you are, their is always someone stronger.
That's all i can think of for now. Now tell everyone what you've learned.