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.
Finally, brothers, whatever is true, whatever is honorable, whatever is just, whatever is pure, whatever is lovely, whatever is commendable, if there is any excellence, if there is anything worthy of praise, think about these things. What you have learned and received and heard and seen in me—practice these things, and the God of peace will be with you.
(Philippians 4:6-9 ESV)
These verses are more than simple positive thinking to get a person through the day. Rather, they are a statement of trust in the sovereign God of the Universe. A genuine trust and rejoicing in God translates into a peace that comes from Christ in our experience – despite the outward situation.
Having a mature spiritual trust in the Lord translates into a life of action prompted by thinking about serving God and those around us in light of God’s sovereignty. A life of selfless service vertically unto God and horizontally towards those around us adds to the life filled with the peace of God Himself.