the seven decisions - andy andrews
If the 4:8 principle is the first book I recommend that changed my life, Andy Andrews, the seven decisions is the second (and only because I read it second). this book contains seven principles that if you follow them, they will literally change your life. you can go through one principle at a time, going through the exercises right then or read straight through and go back and spend time going through the exercises. i go back to this book again and again!
if you've never heard of Andy andrews, let me just say, he is my favorite author of all time! He has an amazing way of brining concepts that you may have heard before in a new light, helping you finally be able to take the steps to apply these life-transforming principles.