Psalm 6:10 Let all mine enemies be ashamed and sore vexed: Let them return and be ashamed suddenly.
As believers we will be under attack. Our battle is not with flesh and blood but Satan and his hosts. We know that in Christ we have victory. All of our enemies will lose and have already lost. They will be turned back. It is Jesus Christ Himself who is our victory.
When we are afraid we must simply trust the One that has done it all for us. He paid our sin debt. He purchased our salvation. We know we have victory because of what He has done for us.