IT'S A SPIRITUAL THING
2 CORINTHIANS 3:5-6 NKJ
5 Not that we are sufficient of ourselves to think of anything as being from ourselves, but our sufficiency is from God, 6 who also made us sufficient as ministers of the new covenant, not of the letter but of the Spirit; for the letter kills, but the Spirit gives life.
When you read the epistles, letters of Paul, Peter, John, and other New Testament writers, you will definitely encounter some spiritual depth. Do not get discouraged if you read a passage or a chapter and stop and wonder if you understand what you read. I have often encountered the same thing. Sometimes, I will go back and re-read a chapter over and over. It helps if you give each chapter some unbroken attention. But even then, there will be parts you just don't get. Don't quit, and whatever you do, don't start saying you just can't understand the Bible. The Holy Spirit is the greatest teacher ever, and He will help you. So, talk that, not your limitations or weaknesses.
Paul understood and conveyed in these two verses that what he had and understood he got from God. God was the One who made him sufficient, not natural talent or intellect.
He also understood that the New Covenant that we have in Christ is a spiritual thing. It's not about keeping Jewish law or what Paul calls the letter. If keeping Jewish old covenant laws would make us right with God, there was no reason for Jesus to come and die on the cross.
No, the new covenant is a spiritual thing. We receive the finished work that Jesus did for us, and we become new creations recreated spiritually. Because no one was able to keep the Jewish laws, these laws pointed to our need for Jesus. Paul knew he was not sufficient in himself, but through Jesus, he became sufficient.
None of us can become right with God on our own efforts or talents. We are made right with God when we receive His Son. This takes bragging rights away from all of us because our being "right" is from God.
The best way we can apply these verses is to thank God for what He has done for us in Christ. To thank Him that He has made us sufficient, spiritually capable. And to not refer to ourselves as unworthy or weak even if we feel this way. It's a spiritual thing that has been done in us, and we are glad.
Thank you, Father, that I don't have to keep Jewish law to be right in your sight. Thank You for what Jesus had done in me and for the spiritual life that I have in Him.