"You cannot do wrong and feel right. It is impossible."
      -Ezra T. Benson

This quote is trying to advice you to do good, to do right. You can't feel good and do bad, or do good and feel bad. If you do good you will feel good, but if you do bad you will feel bad.
-For Example:
   1. If you steal something, you cannot feel good about it.
   2. If you study hard, you will feel good by getting good grades.