Everyone is a sinner, but no one should be proud of it. Our sinful natures lead us into all different types of disobedience against God. Some people spend their entire life mired in such sin. While others, by the grace of God, come out of it. They are changed, forgiven, and saved.
Once a sinner has been “born again” by the Spirit (see John 3:3), they have a new nature that seeks to love and obey Jesus Christ. While sin still rears its ugly head in their life, they are no longer enslaved to it as they were before they knew Christ. Christians have a strong dislike, even a hatred, for their own sin. While being gracious toward others who are still bound up by their sinful natures. And, in an interesting way, God can use our sinful past for glorious purposes in the present.
The Apostle Paul, by his own admission, was once a blasphemous and violent man. He hated Christians and was a well-known persecutor of the church. Yet, in spite of this, he was shown grace. Paul writes, “It is a trustworthy statement, deserving full acceptance, that Christ Jesus came into the world to save sinners, among whom I am chief. Yet for this reason I found mercy, so that in me as the chief of sinners, Jesus Christ might demonstrate His perfect patience as an example for those who would believe in Him for eternal life.” (1 Timothy 1:15-16)
Paul admits to being the “chief of sinners” but he isn't proud of that. What he is proud of is the fact that though he was the “chief of sinners” he was shown mercy. And one of the reasons he was shown mercy was so that “Christ might demonstrate his perfect patience” as a witness to others who would believe. In other words, God used Paul's heinous past sins as a testimony of grace in the present time. God can do the same for you.
Don't glory in your sin, but by all means, glory in the grace that saved you from your sins. And long to be used by God to speak the gospel to others who are enslaved in the same type of sin you once walked in. Who better to witness to a drunk, than a Christian who used to be a drunk? Who better to witness to a violent man, than a Christian who used to be a violent man? Who better to witness to a self-righteous woman, than a Christian women who used to be self-righteous?
Paul was a sinner. But he was a saved sinner. And Paul declared, “By the grace of God I am what I am.” (1 Corinthians 15:10) May the same be said of you.