Do not be anxious about anything, but in everything by prayer and supplication with thanksgiving let your requests be made known to God. And the peace of God, which surpasses all understanding, will guard your hearts and your minds in Christ Jesus.
Pray that we cast all of our cares on God (Psalm 55:22), that we will turn to God instead of anxiety, and that we will be at peace letting Him handle "all these things" as we seek His Kingdom (Matthew 6:33).
from "30 Ways to Pray for Missionaries," compiled by Elaine Helms for the NAMB. (the full list in pdf form is available here)