Must Read: Battlefield of the Mind
This book by Joyce Meyer has changed so many people's lives. She has an adult version of this book but if you are a teenager I would suggest reading this version. I started reading this book in my early teens and I am convinced that if I had not read it long ago my way of thinking would be completely different today and not for the better. I cannot say enough about how powerful the ideas in this book are. It will completely change how you think which will in turn change your life.
This book speaks directly to every person's mind and how it is a battlefield. We are constantly fighting the devil in our minds. When the devil attacks he first attacks the mind with negative thoughts, rebellious thoughts, and tempting thoughts. If we can win the battle of our minds we will live a life of positive thinking that will in turn effect everyone else around us!
Two scriptures that Meyer uses throughout that sums up the book are, "For our struggle is not against flesh and blood, but against the rulers, against the authorities, against the powers of this dark world and against the spiritual forces of evil in the heavenly realms." (Ephesians 6:12) and "For as a person thinks in his heart, so is he..." (Proverbs 23:7)