I find it both fascinating and comforting that even after all this time in ministry, Paul still has a profound sense of his own sinfulness. Paul out of anyone, who is most assuredly guaranteed salvation (and even twice states as much in 2 Cor 1:22 and 5:5), cannot forget his guilt despite the grace he is shown. In fact, he owns it, but perhaps this is what is proper?
When I remember the sinful woman who washed Jesus feet with her tears, I remember Jesus's statement to those who reviled her. A parable told to illustrate the point that those who have been forgiven much love much. Paul has never forgotten who he was or what he has done. He does not try and hide it nor does he deny it. However, he also does not beat himself up over it. No, Paul is a free man, freed through the grace of Jesus Christ. Paul is a man who loved much.
As one moves closer to the light, they begin to realize more and more what darkness has concealed in them. Rather than ignoring his sin, Paul is made more and more aware of the ones he has and consequently more and more aware of how much Christ loved him first. Who could help but fall in love with such a God?