Romans 16:19-20

For the report of your obedience has reached everyone, so that I rejoice over you, but I want you to be wise in what is good and innocent in what is evil.  The God of peace will soon crush Satan under your feet. 

When we are wise in what is good, we gain the knowledge of what it takes to defeat the enemy.  Knowing God and His ways leads to our willing obedience and peace.  We reduce temptations and keep ourselves pure when we are innocent of evil.  Then God will crush Satan under our feet.