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.

Philippians 4:6-7 (ESV)

Through prayer we offer up our requests and appreciation to God and seek guidance and support for all matters to show our dependency on Him. Through prayer we receive the peace and hope of God that is sufficient to calm our fears and worries.