Whatever former things were gains to us, as we thought then, these things, once regarded as advancements in merit, have come to consider as a loss. Absolutely worthless. This is for the sake of Christ and the purpose which He has given our life. Everything is for Him!
This is an act of humbleness. This is not humble-bragging but for the sake of Christ. We consider them worthless because of what Christ has done. It is because of the amazing things that He has done. We will see the glory in it. And, it is unfathomable because of His greatness that can't be explained in words.