Here are some things I learned in life:

That no matter how good a person is, sometimes they can hurt you..
& because of this we must forgive, it takes years to build trust & only seconds to destroy it.. We don't have to change friends if we understand that friends change.. The circumstances and the environment influence our lives, but we are the ones who are responsible for ourselves.. that you have to control your acts, or they will control you.. That patience requires pratice.. That there are people who love us, but simply don't know how to show it... that sometimes the person you think will hurt you and make you fall.. is instead one of the few who will help you get up.. You should never tell a child that dreams are fake, it would be tragedy if they knew.. It's not always enough to be forgiven by someone.. In most cases you have to forgive yourself first.. That no matter in how many pieces your heart is broken.. the world doesn't stop to fix it.. Maybe God wants us to meet all the wrong people first before meeting the right one.. so when we finally meet the right one we are grateful for that gift. 
..When the door of happiness closes, another opens.. but often we look so long at the closed one.. we don't see what was open for us.