I'm a worrier. I worry about things way too much and let myself stress out about too many things. It has always been a big problem of mine. And the verse above is one that I always go back to in my head when I can see that I'm worrying too much. I let it run through my mind along with the passage from Matthew 6:25 and they help calm me down and come to the conclusion that God is going to take care of me.
God knows what is best for us. And not only that, He WANTS what is best for us. We have no reason not to trust in Him. If you have something that you're stressing over or worried about - whether it be financial trouble or family problems or work stress - just "give it to God." Pray about it, talk to Him about it, let Him know what is troubling you and just give it up to Him.
Matthew 6:31 "therefore, do not worry... for your Heavenly Father knows that you need all these things..."