In his chapter on Matthew 6:19-34, Dietrich Bonhoeffer has some excellent things to say regarding the Christian and anxiety. Though the following quotes are longer than normal, they are well worth our read. These are taken from his book The Cost of Discipleship:
They way to misuse our possessions is to use them as an insurance against the morrow. Anxiety is always directed to the morrow, whereas goods are in the strictest sense meant to be used only for to-day. By trying to ensure for the next day we are only crating uncertainty to-day. Sufficient unto the day is the evil thereof. The only way to win assurance is by leaving to-morrow entirely in the hands of God and by receiving from him all we need for to-day. If instead of receiving God’s gifts for to-day we worry about tomorrow, we find ourselves helpless victims of infinite anxiety. ‘Be not anxious for the morrow’: either that is cruel mockery for the poor and wretched, the very people Jesus is talking to who, humanly speaking, really will starve if they do not make provision to-day. Either it is an intolerable law, which men will reject with indignation; or it is the unique proclamation of the gospel of the glorious liberty of the children of God, who have a Father in heaven, a Father who has given his beloved Son. How shall not God with him also freely give us all things?
"Be not anxious for the morrow.’ This is not to be taken as a philosophy of life or a oral law: it is the gospel of Jesus Christ, and only so can it be understood. Only those who follow him and know him can receive this word as a promise of the love of his Father and as a deliverance from the thraldom of material things. It is not care that frees the disciples from care, but their faith in Jesus Christ. Only they know that we cannot be anxious (verse 27). The coming day, even the coming hour, are placed beyond our control. It is senseless to pretend that we can make provision because we cannot alter the circumstances of this world. Only God can take care, for it is he who rules the world. Since we cannot take care, since we are so completely powerless, we ought not to do it either. If we do, we are dethroning God and presuming to rule the world ourselves.
But the Christian also knows that he not only cannot and dare not be anxious, but that there is also no need for him to be so. Neither anxiety nor work can secure his daily bread, for bread is the gift of the Father. The birds an lilies neither toil nor spin, yet both are fed and clothed and received their daily portion without being anxious for them. They need earthly goods only for their daily sustenance, and they do not lay up for a store for the future. This is the way they glorify their Creator, not by their industry, toil or care, but by a daily unquestioning acceptance of his gifts. Birds and lilies then are an example for the followers of Christ. ‘Man-in-revolt’ imagines that there is a relation of cause and effect between work and sustenance, but Jesus explodes that illusion. According to him, bread is not to be valued as the reward for work; he speaks instead of carefree simplicity of the man who walks with him and accepts everything as it comes from God. -178-179
Anxiety is a gospel issue. Let us not forget that. If God is provident, then why do we worry? Worry is for those who have no such God.