Worrying about what tomorrow might bring gets us nowhere. But planning for the future is something we all need to do. Worrying about what I'm going to have for dinner tomorrow is silly. Planning a menu and then going out and buying the necessary food is an activity that will accomplish something useful. Worry is useless.
Concern is helpful.
He tells us what to do. If there is anything you need, pray for it, and that peace of God which is so much greater than we can understand will guard your hearts and your thoughts. Peace is pictured like an armed guard who is standing outside our mind and heart. If anything tries to get in to disturb us, peace blocks the way. Our hearts are kept undisturbed even though there are storms all around us.