Here is another excellent article from Bible Study Tools. This, Why Worrying is a Failure to Grasp the Gospel, is one of the most-read Bible Study Tools articles of 2012, written by Trevin Wax. Visit Trevin's daily blog at Kingdom People (found at The Gospel Coalition).
"I give an inordinate amount of attention to little details. Worry consumes me in a variety of ways: I lose patience quickly, I snap at my wife and kids, or I lose my sense of empathy for others. Worry turns my focus to Me. For a while, I thought that worry was caused by my failure to seek first the kingdom. If I would only fix my eyes on Jesus more, then I would stop worrying. If I would only think about the kingdom more, then anxiety wouldn't be an issue.
"Certainly, those who are seeking the kingdom above all things are not preoccupied with food, and drink, and clothing (as Jesus says in the Sermon on the Mount). And yes, seeking the kingdom first is a good action plan if we find ourselves worrying."
"In these difficult times, we - the people of God's kingdom - need to be reminded of our true citizenship and true identity. The uneasiness of worry surfaces in our hearts when we lose sight of the gospel of God's grace to the undeserving. Failure to grasp the gospel is what causes us to take our eyes off the kingdom and forget who we are in Christ."