It struck me as I read this the contrast between verse 11 and the following verses. Those verses are about those who fear the Lord. This surprises me, because I normally don't associate someone who fears the Lord with someone who has really made a mess of his/her life. A God-fearer is someone who is sin-free - right? Not someone who struggles with addiction. Not someone who has fallen again to lust. Not someone who wrestles with doubt.11 For your name's sake, O Lord,pardon my guilt, for it is great.12 Who is the man who fears the Lord?Him will he instruct in the way that he should choose.13 His soul shall abide in well-being,and his offspring shall inherit the land.14 The friendship of the Lord is for those who fear him,and he makes known to them his covenant.15 My eyes are ever toward the Lord,for he will pluck my feet out of the net. (Psalm 25:11-15, ESV)
That's not what David thought, because he begins these verses with a confession that his guilt is great. Not just that he sinned - his confession is that his sin is great. On the other hand, the following contemplation about the blessings that fall on those who fear God are an evident reflection of David's own experience. So those who fear the Lord and those who have messed up are categories with non-empty intersection. David certainly experienced both - at the same time!
This doesn't mean that fearing the Lord has no ethical implications. In Scripture, those who fear God are those who love and obey him. But fearing God is not essentially about where we've been - or even perhaps where we are - it is about where we are going. Those who fear God may really mess up, but they are looking toward the Lord (verse 15). That's the direction of their life.
What makes this possible? Grace! We can confess our sin while simultaneously pressing on to know the Lord because of what Christ has done for us. It is not because we are good for Jesus, but because Jesus was good for us that we can know the friendship of the Lord, even while weeping over our sins. John put it this way:
6 If we say we have fellowship with him while we walk in darkness, we lie and do not practice the truth. 7 But if we walk in the light, as he is in the light, we have fellowship with one another, and the blood of Jesus his Son cleanses us from all sin. 8 If we say we have no sin, we deceive ourselves, and the truth is not in us. 9 If we confess our sins, he is faithful and just to forgive us our sins and to cleanse us from all unrighteousness. (I John 1:6-9, ESV)Yes, we must walk in the light - but note that those who walk in the light are the same people who are confessing their sins. What makes this possible is the reality that those who know Christ are both just and sinful at the same time,“Simul Justus et Peccator,” as Martin Luther put it, because Christ took our sins, bore them on the cross, that we might have his righteousness.