It is important for us to understand that we have blind spots. True saints have blind spots. Our fallen nature has the ability of convincing ourselves that wrong is right. God directed David to write here of the importance of understanding that we are not good judges of our own errors. The Hebrew word translated as “errors” speaks of “moral mistakes”. We need God to show us our errors and we also need God to cleanse us of our secret faults.
David had tried to keep his moral mistakes secret. It was not very secret. David had several wives before he lusted after Bathsheba. He tried to keep that situation secret, but Bathsheba was with child. Thankfully David did not counsel her to murder that baby. He did try to get her husband to come home and spend time with her so that he could cover for that baby she was carrying. Uriah was a godly man and a man of honour. He was not going to come home from the battle and enjoy married life while his fellow Hebrews were out risking their lives to advance against the enemies of God.
David tried to deal with his “secret” by having Uriah killed in battle. Joab knew about David’s plot. The nations around Israel would figure out there was something not right about the timing of the birth of this child. God intervened and prevented this disaster from being worse than it already was.
After almost a year of trying to bury this sin, David finally dealt with it. He needed God to cleanse him from his secret faults. He could not clean this mess up on his own. God was gracious to him and did forgive him. However, David had also given occasion for his own family to express their immorality because of this failure on his part.
In verse 13 David prayed that he would be kept from presumptuous sins. The Hebrew word translated as “presumptuous” means “arrogant”. It is much better for us to avoid sin, than to have to deal with the consequences of sin later. It is important that we have that humble heart that will keep us from assuming that our sinful intent is no big deal. Jesus taught us that thinking sinful thoughts is the same as committing sinful acts. We need God to guide us so that we do not yield to temptation. We need to have God guide us so that we change our way of thinking so that we do not assume we can commit certain sins without consequences.
David prayed that these presumptuous sins would not have dominion over him. David was being reminded here by God of just how powerless we are to fight the flesh. We need to turn to God and we need Him to change us so that we have a strong conviction of the wickedness of any sin.
There is no such a thing as a “white lie”. I have heard the statement more than once: ‘it is easier to ask for forgiveness than to ask permission’. That statement may sound good, but it really has no place in the Christian life. I am as human as the next person. This prayer that David is making is an important prayer for me as well as any other true saint. We need God to keep us from our sinful pride. We need to ask God to reveal that root within us and we need to follow Him in confessing that sin and setting up His defence against it.

I Corinthians 10:12 Wherefore let him that thinketh he standeth take heed lest he fall.
13 There hath no temptation taken you but such as is common to man: but God is faithful, who will not suffer you to be tempted above that ye are able; but will with the temptation also make a way to escape, that ye may be able to bear it.

David further stated that in order to be upright, we need to deal with this very real part of human nature that cannot be allowed to dwell in the true believer’s life. We need to be innocent from the great transgression.

James 1:15 Then when lust hath conceived, it bringeth forth sin: and sin, when it is finished, bringeth forth death.

There is a progression that takes place in a saved person’s life, when we entertain sin. Paul talked of putting the old man to death. He also pointed out that there is that constant need to be vigilant against the subtle nature of the old man. James tells us that we need to be aware of the progression that is all too real. Unless we are walking in the Spirit as God’s redeemed people, we will try to ignore the root of sin and it will bite us hard. We need to be aware of how absolutely dependent we are upon God’s grace once we are His child.
David was directed to close this Psalm with the prayer that his words and the meditation of his heart would be acceptable to the all knowing and all seeing LORD. He is the strength and He is the redeemer of every true saint.
The apostle Paul wrote:

Philippians 4:13 I can do all things through Christ which strengtheneth me.