Sinless or repentant sinner?

Though you probe my heart and examine me at night, though you test me, you will find nothing; I have resolved that my mouth will not sin. The Holy Bible, A Prayer of David, Book of Psalm, chapter 17 verse 3

I think *we* (those who are believers in God and those who want to mock believers of God - so pretty much everyone) make a mistake with the last part of this quote.  I think we think that to claim that God will find nothing and our resolution is to not sin that it, and David, means "sinless".  I'm pretty sure it doesn't.  Here's what I do think it means; I think it means that we should be sensitive to sin so that the moment we fall into it (and we ALL fall into it, none of us are exempt from sin) - through word or action - we are quick to repent.  I think it means that we invite the probing of God in our lives and we are quick to repent for what surfaces when he probes.  It doesn't mean that we are sinless, it doesn't mean that David thought he was sinless.  When non-believers mock believers and try to accuse us of believing we are perfect it is a weak argument at best.  We don't think that and those who might think that don't have very many people, if any, that would back them on their claims.  Listen.  I sin.  I do.  But I am usually pretty quick to catch it.  And in part because I have invited God to examine me, not just at night but all the time!  And he does.  He is quick to point out when I have sinned and how I need to make it right.  And until I make it right I am pretty unhappy.  So because I am pretty good about allowing his examination to bring repentance I can say that I am resolved to not sin.  I can say that I hope nothing sinful is found in me when I am examined because if I've repented then I'm clean (for the moment anyway!).  

What about you?  How have you thought about this particular quote before?  (There are a few others like it and I would use the same thoughts with those as well)  Are you open to seeing this in a different way than you have before or may have heard it taught before?  Or has this been your view on it as well?