While most commentators divide Matthew 6:19-34 into at least four sections (19-21;22-23;24; 25-34), I tend to think they should be treated as a whole.
"Do not store up for yourselves treasures on earth, where moth and rust consume and where thieves break in and steal, but store up for yourselves treasures in heaven, where neither moth nor rust consumes and where thieves do not break in and steal. For where your treasure is, there your heart will be also.
"The eye is the lamp of the body. So, if your eye is healthy,your whole body will be full of light, but if your eye is unhealthy, your whole body will be full of darkness. If then the light in you is darkness, how great is the darkness.
"No one can serve two masters; for a slave will either hate the one and love the other, or be devoted to the one and despise the other. You cannot serve God and wealth.
"Therefore I tell you, do not worry about your life, what you will eat or what you will drink, or about your body, what you will wear. Is not life more than food, and the body more than clothing? Look at the birds of the air; they neither sow nor reap nor gather into barns, and yet your heavenly Father feeds them. Are you not of more value than they? And can any of you by worrying add a single hour to your span of life? And why do your worry about clothing? Consider the lilies of the field, how they grow; they neither toil nor spin, yet I tell you, even Solomon in all his glory was not clothed like one of these. But if God so clothes the grass of the field, which is alive today and tomorrow is thrown into the oven, will he not much more clothe you--you of little faith? Therefore, do not worry, saying, 'What will we eat?' or 'What will we drink?' or 'What will we wear?' For it is the Gentiles who strive for all these things; and indeed your heavenly Father knows that you need all these things. But strive first for the kingdom of God and his righteouness, and all these things will be given you as well.
"So do not worry about tomorrow, for tomorrow will bring worries of its own. Today's trouble is enough for today." (Matthew 6:19-34) (NRSV)
The core thesis comes late in the passage: "But strive first for the kingdom of God and his righteousness, and all these things will be given you as well." To be frank, this is the central thrust of the entire Sermon on the Mount. Paraphrased, it might go something like this: "Devote yourself solely to God; all other things will then find their proper place."
Such a perspective clears one vision, so to speak. We see clearly the source of our life (God), our family (all others), our home (the creation), and our direction (love). Any lesser perspective clouds our vision and leaves us to walk in gathering darkness.
In such darkness we fixate on trying to secure our security (storing up treasures, whether of gold, expertise, reputation, etc.). We fail to see how all such treasures are prone to decay or loss, indeed that loss is inevitable. In effect, we wind up trying to walk two paths at the same time, serve two very different masters at the same time (God or our own anxiety). As Jesus says, such a double-visioned approach to life does not work. In the end, we opt for one option or the other.
Like any good teacher or preacher, Jesus illustrates his point with particular examples, hence his injunctions not to worry about food, drink, clothing and the like. Such worry turns out to be futile and betrays a nagging tendency to trust in ourselves (or other providers) rather than in God. More importantly, indulging such worries pull us toward dependence on "wealth." We find the allure of its promise of independence from dependence on God or others too much to resist, and we give it our worship. And both of us know what our traditions have to say about idolatry!