Says Fowl, "The peace of God surpasses the unbelieving mind, which is full of anxiety because it cannot think higher than itself." He goes on to quote Thomas Aquinas' comment on the peace of God.
"As the peace of God exists in heaven, it surpasses all the knowledge of the angels. As it exists on earth it surpasses all the knowledge of those who lack grace."(Fowl, 184)
According to Paul, freedom from anxiety comes only through prayerful, grateful acknowledgement of one's dependence on God. (Fowl, 183) The Philippians can be free from anxiety because the Lord is near (4:5). They can call on God in prayer and with thanksgiving.
This is the peace of God Paul proposes as an alternative to anxiety. The Philippians are not called to imitate the peace of Christ, but to accept the gift of that peace being offered to them by the Grace of God, accessed through the habit of prayer.
"Let's do this!" is not a good motto if we take it as a call to banish our anxieties by sheer will power.
"Let's do this!" is a good motto if we think of it as God through Christ speaking to us in the midst of our anxieties.
When we tire of the endless struggle to master our anxiety by summoning our own inner resolve, let's acknowledge that we've come to the end of our human abilities and need to call for help.
Let's call Somebody!