What does Psalm 40:12 mean?

The Bible describes David as a man after God's heart (1 Samuel 13:14; Acts 13:22), but that does not mean he was perfect or sinless. David held no such illusions, either. Here he admits he is a sinful person. Rather than blaming God for difficulties in his life, David accepts that many hardships—but not all (John 9:1–3; 1 Peter 3:17)—are brought on by our own sin. These errors have caught up to David and surrounded him.

In dramatic terms, David claims he is so distressed by his own mistakes that he cannot see clearly. If David would try to count his sins, he would not be able to do so because they are too many to count. He confesses that they are more than the hairs on his head. He feels as though his heart has left him.

We cannot count our sins, because they are innumerable. Not only are we guilty of sins of commission but we are also guilty of sins of omission. We do what we should not do, and we do not do what we should do. James 4:17 says, "Whoever knows the right thing to do and fails to do it, for him it is sin." David acknowledged his sins, and we should too. Confession is an essential step toward forgiveness.