 Because they trust in you. How do you have that? How do you have a steadfast mind? You trust in the Lord. You spend more time in his word than you do scrolling or even watching the updates this weekend from the horrific shooting at the Trump rally. You will keep in perfect peace those whose minds are steadfast because they trust in you. It doesn't mean you ignore what's happening. It means you give more time to your Savior, the one who's always in control, even when the world seems completely out of control.