There are places in Scripture that I return to often. The forth chapter of Philippians is one of those places. Everyone at times experiences physical and emotional suffering, trials and tribulations... Circumstances that test our faith in God's providence. If we allow them to, these circumstances can steal the joy and peace that God has promised us in Christ.
This special joy and peace the Christian has in Christ is not just superficial happiness and contentment that comes and goes depending upon our circumstances. Nor is it a result of a positive mental attitude produced in our own strength and discipline. This is super natural joy and peace that God provides to His children who trust and obey Him.
You have probably personally experienced it and have seen other Christians who are rejoicing and have "peace that passes understanding", even through the most difficult of circumstances. We have heard unbelievers say; "Either they just don't understand their situation or they know something we don't know." That something they don't know is that "The Lord is near"!
If we really believe that God "is and that He is a rewarder of those who seek Him" (Hebrews 11:6b), then we can have His joy and peace regardless of our circumstance. Why? Because "...we know that God causes all things to work together for good to those who love God, to those who are called according to His purpose." So I go back to Philippians 4 often where we are reminded how to secure this amazing, super natural joy and peace given to us by God, our Father.
First, remember "the Lord is near"! He has promised to "never leave or forsake us". Next, we are to "be anxious for nothing, but in everything by prayer and supplication with thanksgiving, let your requests be made know to God". Then, we are to think about those things that are honorable, pure, lovely, excellent, things worthy of praise. We are to let our minds "dwell on these things" understanding that God loves us and that He is in complete control of everything. When things seem out of control and we can't see how it is all going to work together for good, we need to be "walking by faith and not by sight" (2 Corinthians 5:7).
Not only are we to cease worrying about anything, be praying about everything and thinking godly thoughts, we are to do the right things. When circumstances are difficult, the temptation is great to lean on our own understanding rather than fully trusting and obeying the Lord. But when we do fully trust and obey Him, He promises "the God of peace will be with you". And "Who will separate us from the love of Christ? Will tribulation or distress, or nakedness, or peril, or sword?...But in all those things we overwhelmingly conquer through Him who loved us." (Romans 8:35,37). Maranatha!