The truth about happiness.

What's behind the truth of happiness, yes, that's sadness. Example: A girl likes a guy. She confessed to the guy. The guy broke her heart because he likes another girl that she hates. That girl cried for days and days. Then the guy dumped the other girl and fell for that girl. They become best friends at first, then that guy told her that he loves her. She felt very happy and said : "I love you." Then you know the story and I don't want to make it longer now.