Prayer starts with thanksgiving, thanking God for all He has done. Sometimes this is hard to do, but thanksgiving helps our prayer. But this verse starts by telling us to be careful for nothing, that is, don’t worry about anything, just pray. Then it says to just let God know what’s going on, just talk to God. Then after all these items, there is the peace of God that goes beyond what we think and feel. This peace guards our hearts by filling us with the peace of God.
Philippians 4:6-7 Be careful about nothing; but in everything, by prayer and supplication with thanksgiving, let your requests be made known to God; 7 and the peace of God, which surpasses every understanding, shall guard your hearts and your thoughts by Christ Jesus.