Naruto - To never give up, how valuable friendship really is
Sasuke - Hatred boils inside all of us but love always trumps it; revenge isn't the answer
Sakura - ... Cry and let others do things for you
Hinata - You can accomplish great things.
Rock Lee - No matter the obstacles, persevere and you will succeed
Kakashi - Learn from your mistakes (*cough*Rin and Obito*cough*)
Itachi - We must all make hard decisions in our life and how we chose them determines the future
Jiraiya - Everyone has potential and peace is the greatest thing ever
Rin - If you ever friendzone anyone (boy or girl), expect them to change the world
Hashirama - If you ever fight an Uchiha make sure they die; give the spot for leader of a nation to the Uchiha
I might write more later