“Submit yourselves, then, to God. Resist the devil, and he will flee from you.” (4:7)
According to this verse it is really quite easy for a Christian to defeat the Devil. All you have to do is resist his temptations, and he will run away.
This does not mean, of course, that we can defeat the Devil by our own strength, cunning, and power. Remember, we also have to “submit… to God.” God is the one who actually defeats the Devil for us. But we cannot just sit back nonchalantly and watch God work. God demands that we become active participants in the battle. This is not so that we can take any credit for our victory. Rather it is so our heart and soul become fully dedicated to serving God.