David was afraid of the Ark - and of God! Let us notice, however, that God did not rush down and give David the answer. He did not say, "David, do you see what you have done wrong?" He did not explain to David just why He struck Uzzah. He made David work through the problem.
He does the same thing with us. When we find that we are out of sync with God, He does not simply rush to intervene and say, "Now there, there, my son." He does not pat us on the head and say, "You are alright."
Rather, He says, in effect, "Now do you understand that you are in hot water?" He asks, "Are you feeling pain?" And you say, "Yes!" Then He says, "Well, can you figure out why?" So we have to do that.
Upon close examination, we find that those who had advised David were complacent and neglectful. They thought that, because the Ark came to them on a cart from the Philistines, they could simply send it on to where it was supposed to go in the same way. Obviously, that did not work out so well!
The instructions for how to carry the Ark properly are found in I Chronicles 15:2, 14-15. These instructions were learned correctly because David had to work his way through the problem.
Can we make mistakes like this? David was "a man after God's own heart"! Of course we can! David made mistakes left and right, yet God loved him. When God puts us through such things, it does not mean that He does not care for us. David committed adultery with Bathsheba; killed Uriah the Hittite; caused the death of thousands and the death of his son, Absalom. All because he, at times, took God's laws for granted.
We, too, can become complacent and neglectful as to how we live our lives. If we do not respond to God, He will increase the pressure on us.
Leviticus 26 and Deuteronomy 28 are the "blessings and curses" chapters of the Bible. Consider these in light of the increasing pressure that God applies to draw us closer to Him and to stop taking Him for granted.