The words Jesus spoke here don't imply that we should not provide for our basic needs by doing honest work. There are many scriptures that prove diligent, hard work is our responsibility and most beneficial to us. Proverbs 12:11 says those who work with their hands will have abundant food and those who don't have no sense. And 1 Timothy 5:8 says providing for our families is our obligation. Jesus was pointing out that no matter how faithful and diligent we are in taking care of and providing for our physical well being, that provision is only necessary and of value for a season. At some point our time here on earth will come to an end and that natural provision will loose all worth. That's why investing our time and efforts in spiritual things is most beneficial, because the fruit of that kind of labour will last for eternity. Once we have committed our lives to Christ, diligently spending time feeding on the truth of His Word and obeying the voice of His Holy Spirit within us, will have lasting significance. No time or effort spent in God's Word or in His presence will be for nothing. Every act of obedience will have eternal consequence and a value more weighty than gold. Jesus is showing us that in all we do, keeping Him and His ways our priority, is the greatest investment we can possibly make.