James 4:7-8
7Submit yourselves, then, to God. Resist the devil, and he will flee from you. 8Come near to God and he will come near to you.
All you need to do is put your full faith in Christ Jesus, think about the heavenly things, and do as the Spirit convicts. How do you defend yourself? Don't, let God do it. Yes, equip yourself with the armor of God...because that is what is saving you...not the fact that you put it on.