Isaiah 26:3-4

You will keep in perfect and constant peace the one whose mind is steadfast (that is committed and focused on You-in both inclination and character), because he trusts and takes refuge in You (with hope and confident expectation). Trust (confidently) in the Lord forever (He is your fortress, your shield, your banner), for the Lord God is an everlasting Rock.

Our minds can be a battlefield if we don’t guard our thoughts. The enemy will send darts where we have weakness and cause faith to falter if allowed. Perfect and constant peace comes from our reliance on God and His direction in the word. God is more than a symbol for us but our shield and fortress, and God genuinely want to help us keep the peace.