this is kind of the backwards version of "13 Going on 30".
One morning you wake up, and you're back in your childhood bedroom. When you look into a mirror, you're met with the reflection of your twelve year old self. You have gone back in time, but you remember everything that you know at whatever age you are now. So:
What is your first reaction? How do you treat your family and friends? What do you do differently with your life?