1 Corinthians 15:9For I am the least of the apostles, unworthy to be called an apostle, because I persecuted the church of God. 
One of the most amazing things that Christ affords us as Christians, is the ability to live with great gratitude.  Not only in the saving of our souls from damnation, but in  finding forgiveness and mercy, in the things we have great regret for, and remember for the rest of our lives…
“Remembering” the things we greatly regret, versus being “imprisoned” by the things we regret, is what the power of the Holy Spirit frees us from living in.  To be in bondage of the past sins we’ve committed, is to contradict living free in Christ and experiencing abundant life in Him!
The apostle Paul  in his “remembering” of his past sins against the church, is not faux humility, but a deep regret, that pushes Him deeper in the appreciation of God’s grace to be called an apostle.  It was his regret and remembrance, that caused him to work hard in God’s call, not to “work off his sins”.  But work hard, from a place of deep gratitude in spite in of our sins, that’s the gospel of grace! (1 Corinthians 15:10)
Since being in ministry, I watched countless “church goers” count themselves out, because they have past or present sins, that they think “cancels them” out from being useful.  When in reality, it is those sins that should push us deeper in the amazing grace and mercy of God, to use us in spite of our sins!
Usually it is self-righteousness that keeps us from confessing sin and remembering it, so Christ can get all the glory for us being useful.
In His Love, Ld