We do not need to fear the enemy, including when he seems relentless and our defense doesn't seem to be working. Truthfully speaking, the enemy lost at the cross. He lost the war, but he doesn't like to give up in the battle. How much more should we, who won the war in Christ, not give up in the battle? Why do we say, "Oh well. Jesus won the war, so who cares if we lose this battle?"
He may have found you as a wretched sinner in the mud of your sin, but he cleansed you by the blood of his Son Jesus, raised your dead spirit to life and filled you with the Holy Spirit of the living God. Walk in the goodness and victory of your salvation!