1 Corinthians 15

As Paul was teaching the doctrine of the Resurrection, I was touched with his remarks concerning himself -

"For I am the least of the apostles, that am not meet to be called an apostle, because I persecuted the church of God." (New Testament | 1 Corinthians 15:9)

I sense that Paul, remembering that at one time he was somewhat rebellious felt that that maybe he was not as qualified or worthy as the other Apostles that may have been more faithful during the Savior's ministry. For some reason, I could relate to that. But knowing this, Paul then explains -

"But by the grace of God I am what I am: and his grace which was bestowed upon me was not in vain; but I laboured more abundantly than they all: yet not I, but the grace of God which was with me." (New Testament | 1 Corinthians 15:10)

Paul is then saying, but nonetheless, he was chosen and been called to this sacred Holy calling. And remembering his days of rebelliousness and the mercy of the Savior, he felt an even stronger desire and need to labour more abundantly to prove himself worthy. Again, I seem to understand this deep desire.

But understanding the call as a apostle or especial witness came from the Lord, Paul understood that -

"...whether it were I or they, so we preach, and so ye believed." (New Testament | 1 Corinthians 15:11)

God's called representatives are entitled to the Holy Ghost if they remain worthy, faithfuland, and magnify their callings. Therefore, as Paul states, it does not matter what happend in the past. What does matter is -
"What I the Lord have spoken, I have spoken, and I excuse not myself; and though the heavens and the earth pass away, my word shall not pass away, but shall all be fulfilled, whether by mine own voice or by the voice of my servants, it is the same." (Doctrine and Covenants | Section 1:38)