Have no anxiety 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 passes all understanding, will keep your hearts and your minds in Christ Jesus. (Philippians 4:6-7)

St. Paul is telling us that God wants us to share our lives with him. From small things to big things, from happy events to the saddest events of our lives, we are to talk to the Lord, to pray and give God thanksgiving.  For there is purpose to our prayer, beyond the specifics that we are praying for. When you read verse 7 with a heart open to the truth, you will understand that the only source of true peace is God, and we need to receive that peace so we can keep our hearts and minds focused on Jesus.