Jesus knew how worries and anxiousness can destroy joy in the lives of people and therefore teaches us in Mathew 6:34 to meet each day's challenge as they come. It is very difficult to rejoice in life when we are facing trials, pain and sufferings of this world. Paul was in prison when he wrote a letter to the Philippians in Philippians 4:4 encouraging them to "Rejoice in the Lord always.” Paul was not a man who did not experience sufferings and trials. Infact he tells his story in 2 Corinthians 11:22-27 about the many trials he faced. Why would he then write to "Rejoice in the Lord always"? Paul was reminding us of the work Jesus Christ did on the cross for us. He was making us understand that Jesus has overcome the tribulations of this world; therefore, in the midst of whatever trial we may face we should rejoice. We need to understand that joy is not an emotion or feeling of happiness. Jesus mentioned in John 15:11 that Himself is Joy; and therefore as we put our trust in Him and His promises, His joy will remain in us in abundance. We must therefore have this assurance that whatever challenges we may face in life, God's strength; which is His joy is in us to see us through. Jesus has already paid the price for all of our sufferings. All He wants from us is to trust Him and Surrender all our burdens unto Him. The price for all our sorrow, pain, suffering, stress, anxieties are all paid for. Why not just trust in the Lord and His promises and see Him working on your behalf.
God is so mindful of you and He loves you.
1 Thessalonians 5:16