Answer:
Use me to reward good behavior.
I belong to everyone. Sometimes make you happy, sometimes make you sad. I will never end until the day you do. What am I?
I fill a room but take no space. What am I?
I am heavy forward but backward I am not. What am I?
I've been argued on my color. Without me you'll die. So many attempts on your life use me so make sure you have many of my White friends.
What do you purposefully put lots of in and on your body, but run away from when you encounter it outside?