Seek First His Kingdom
Jesus had been exposing the foolishness of worrying (Matthew 6:25-32). He said that worry cannot change anything; it cannot extend your life; and it demonstrates your lack of faith, showing that you do not trust Your Heavenly Father to provide for His children. Worry is a part of the normal pagan mind-set, which excludes the care of a loving God and assumes that human effort alone will achieve the answer to every problem.
Worry points to the inadequacy of self or the uncertainty of any help from outside. The worrying person certainly tries hard to fix everything, and yet despair and not hope is the default end-point. Jesus said that instead of striving to arrange the future, we should trust that God has already arranged the future for His people in His kingdom. It is in seeking the welfare of His kingdom that we will find our own rest. But what does that mean? Can we somehow by our efforts create heaven? No! Of course not!
Jesus meant that if our hearts desire is for His will to be done, and if we contribute to that by obeying what He says (that is practical righteousness - doing what is right), then the Lord will give to us all that we need: food, drink, clothes and all necessary material possessions. That does not mean that He will give us all we demand, or deliver according to our timetable; but He will provide in just the right way and in time.
Worry is always about the uncertainty and insecurity of the future (of the future consequences of the past). Until Jesus comes back there will always be a 'tomorrow', but let Him look after every 'tomorrow'. Our job is to do what is right today and pray that His will is done and His kingdom will grow today and tomorrow. Worry can so easily become a habit, but it is not a godly habit. We should repent of such unrighteousness and ask the Lord to help us to trust that He does know what He is doing, and He will do it well ... for us, for our family and friends and for the building of His kingdom.