"Do we need to stop at Wal-Mart for school supplies?"
Getting an answer to a question like this from my son always feels to me like pulling teeth. So today I tried a picture. Think of yourself as a body with you inside, your "soul."
Now think of your soul having three parts: a mind that thinks, feelings, and your will. Your will is the part of you that makes choices, that makes the decisions. Your will can go with your feelings or your will can go with your mind.
So let's say your mind knows you need paper for school but your feelings don't want to go to Wal-Mart. Your feelings want to go home and watch TV or play Call of Duty. Your will is what makes the decisions.
The person who turns out to be happiest in life is the person whose will chooses with their mind and what they know is the thing they should do.
Of course all these things--mind, feelings, and will--are ultimately functions of the brain which is part of the body. What function a detachable soul might play is the stuff of fun discussions. These are true pictures, not literal ones.