You will keep him in perfect peace, whose mind is stayed on You, because he trusts in You. (Isaiah 26:3)
There is no peace outside of God’s will, but only a false sense of security. If you want peace, you need to stay connected to God. You cannot do that while only believing some of what He says; you must embrace every thought He sends into your life, acknowledging His plans for you as greater than your own and existing for your own good. That is what it means to trust in God.