The following excerpt is from John Piper his weblog:

Think of this, you are a blacksmith making horseshoes. You are hammering on a white hot shoe and it ricochets off and hits you in the leg and burns you. In your haste to tend to your leg you let the shoe alone unfinished. You wonder why God let this happen. You were singing a hymn and doing his will.

Your helper, not knowing the horseshoe was unfinished gathered it up and put it with the others.

Later there was an invasion of your country by a hostile army with a powerful cavalry. They came through your town and demanded that you supply them with food and with shoes for their horses. You comply.

Their commander has his horse shoed by his own smith using the stolen horseshoes, and the unfinished shoe with the thin weak spot is put on the commander’s horse.

In the decisive battle against the loyal troops defending your homeland the enemy commander is leading the final charge. The weak shoe snaps and catches on a root and causes his horse to fall. He crashes to the ground and his own soldiers, galloping at full speed, trample him to death.

This causes such a confusion that the defenders are able to rout the enemy and the country is saved.

Now you might say, well, it would sure help me trust God if he informed me of these events so that I would know why the horseshoe ricocheted and burned my leg. Well maybe it would help you. Maybe not.

God cannot make plain all he is doing, because there are millions and millions and millions and millions of effects of every event in your life, the good and the bad. God guides them all. They all have micro purposes and macro purposes. He cannot tell you all of them because your brain can’t hold all of them.

Trust does not demand more than God has told us. And he has given us immeasurably precious promises that he is in control of all things and only does good to his children. And he has given us a very thick book where we can read story after story after story about how he rules for the good of his people.