Humans are often saddled with worry. We can be worried about many things - our health, our wealth, our family, our friends, our reputation, our church, this and that.
Whatever we worry about, our worries aren't really about that thing - our worries stem from our desire for power. That's the first and greatest sin - you will be like God. We hear that and think, "Ah ha! Then I will have power to make things be how I want them to be." Sinful man lusts for power.
And then, we see that we don't have it. And thus, we worry. My body fails, and I can't fix it. The economy goes in the tank and the creek is rising - and I can't fix it. My family is full of people who are off doing foolish things - and I can't fix it. My friends keep making a mess of things - and I can't fix it. Vile rumors are spread about me - and I can't fix it. The Church is beset upon all sides by the tyranny of wicked men - and I can't fix it.
Our Lord tells us that we are to seek first His kingdom. You know - Seek ye first the kingdom of God and His righteousness, and all these things shall be added unto you (how many of you started humming while reading that).
He doesn't tell us this to give us power. He doesn't tell us the secrets to how we can get all the things we want added unto us. He tells us to turn away from worry, from our sinful desire for power and simply let God be God, let God reign in His kingdom -- and He will care for you in a way that is good for you. Not necessarily what you will, but in the way that He wills for you, which is good.
We want power - we don't have it, and so we worry. Beat down your desire for power, look to Christ, delight in His righteousness for you and His forgiveness, and it's not that the worries you have will go away - it's that you will learn to worry about them less.