I am sinful. Sin is a serious--gravely serious--matter. Recall that Paul wrote of himself near the end of his life that "Christ Jesus came into the world to save sinners, of whom I am the foremost" (1 Tim. 1:15). The immediate observation is that the words for himself are in the present tense; Paul continued to see himself as the "chief of sinners." Yet he writes in that same passage about God's grace coming to him. Paul received Christ's mercy (vv. 12-17). Credit is given where credit is due--Paul as a sinner, Christ as his Savior.
This is tough because we don't have much recorded about Paul's regular struggles. We see repentance at his encounter w/ Jesus on the road to Damascus (Acts 9) and there may be one other instance in Romans 7, but besides that there really is no recording of Paul's "sins." However, Paul did not see himself as the foremost sinner merely because of past sins, nor was it because he was struggling with blatantly sinning, taking his salvation for granted and living some kind of outlandish lifestyle in complete opposition to God though claiming to be a Christian.
I believe Paul saw in his heart utter corruption beyond self-repair. He knew only Jesus could restore him, that Jesus was, is, and forever will be the only human being to ever walk the earth who was capable of changing his heart and all our hearts. Paul saw his life as an example of God's power, writing, "I received mercy for this reason, that in me, as the foremost, Jesus Christ might display his perfect patience as an example to those who were to believe in him for eternal life" (v. 16).
What Paul knew, I must know. Like Paul, I do not lose my identity while I am on this earth. I am the one created in the image of God, who, marred by sin in every way, is known as "a sinner." This truth is coupled with the glorious reality that my identity is also completely wrapped up in Christ's life-saving, merciful, perfectly gracious work to where I am also one who is "saved by grace." So here and now, in every day that I walk on this earth, I am a person whose identity is found in sin, but more so in salvation from that sin because of Christ.
I am Andrew, a sinner saved by grace.