As sinners we all become way too comfortable with our sin. The thought that once bothered becomes an action that no longer plagues our conscience. The word that troubled us the first time it was uttered now is accompanied by others that are worse. The marriage that was once a picture of biblical love has now become a relationship of cold-war detente. Commitment to work degenerates into doing as little as we can for as much pay as we can negotiate. A commitment to a devotional life becomes perfunctory and empty duty, more like getting our ticket punched for heaven than enjoying communion with our Lord. Minor, unexpressed irritation, which once troubled our hearts, is now fully expressed anger that is easily rationalized away. Sin is like the unnoticed drips of water that silently destroy the foundation of a house. You see, we all have a perverse capacity to be comfortable with what God says is wrong. So God blesses us with violent, uncomfortable grace. Yes, he really does love us enough to crush is, so that we would feel the pain of our sin and run to him for forgiveness and deliverance. David says, "Let the bones that you have broken rejoice." You wouldn't say, "Hooray, I have a broken bone!" But that is very close to what David is saying. He is using the searching pain of broken bones as a metaphor of the pain of heart you feel when you're really see your sin for what it is. That pain is a good thing.
Think about it: this physical pain of an actual broken bone is worth being thankful for because it's a warning sign something is wrong in that arm or leg. In the same way, God's loving hammer of conviction is meant to break your heart, and the pain of heart you feel is meant to alert you to the fact that something is spiritually wrong inside of you. Like the warning signal of physical pain, the rescuing and restoring pain of convicting grace is a thing worth celebrating.