The veil over Moses' face

Contemplating on the veil Moses put on his own face, Paul came up with an unexpected conclusion.
When Moses brought the Old Covenant down from Mount Sinai, his face was shining in brightness as a result of conversing with God. He had to cover his face with a veil (Exodus 34:33). The sight was glorious enough for the Israelites. But Paul understood it differently. He argued that this brightness on Moses' face was fading!
Why was Paul so bold as to claim that the brightness on Moses' face was fading. It was because Paul had seen a greater splendour --- Jesus.
Indeed, in this case, what once had splendor has come to have no splendor at all, because of the splendor that surpasses it (2 Corinthians 3:10).
The New Covenant came with a greater splendour because it is a dispensation of righteousness while the Old Covenant was a dispensation of condemnation. It is well known that Paul had a rather negative view on the Law of Moses which defines what sins are and therefore it condemns rather than justifies. Moreover, nobody would be able to observe the Law of Moses in its totality. Therefore, it was hopelessly impossible to be justified by simply observing the Law.
Moses put the veil on in order that the Israelites might not see the fading splendour on his face (2 Corinthians 3:13).
The splendour of the Old Covenant was outshone by the New which was the gospel Paul was preaching. Paul constantly emphasized that this gospel did not come from man but from God. The preaching was commissioned by God not for his personal gain but for the good of the listeners.
For what we preach is not ourselves, but Jesus Christ as Lord, with ourselves as your servants for Jesus’ sake (2 Corinthians 4:5).
For Paul, this gospel, this "light of knowledge of the glory of God" (2 Corinthians 4:6) is a treasure which was the transcendent power of God (2 Corinthians 4:7). Possessing this treasure allowed him to undergo all sorts of sufferings.
We are afflicted in every way, but not crushed; perplexed, but not driven to despair;
persecuted, but not forsaken; struck down, but not destroyed;
always carrying in the body the death of Jesus, so that the life of Jesus may also be manifested in our bodies (2 Corinthians 4:8-10).
Paul spoke like a giant towering over us, a giant animated by the life of Jesus. What sustained Paul among these sufferings? I think it was because Paul saw a greater meaning in these sufferings.

1. It is for the sake of Jesus.
   For while we live we are always being given up to death for Jesus' sake, so that the life of Jesus may be manifested in our mortal flesh.
   So death is at work in us, but life in you (2 Corinthians 4:11-12).
   The life of Jesus continued and was manifested in the sufferings (death) they encountered in evangelization. In bringing about the transformation of the lives of many, a price (death) had to be paid. This brings up the second point --- life in you.
2. It is for the sake of the Corinthians.
   This theme of suffering for their sake has been brought up many times in this epistle (1:6, 2:4, 3:18 and 4:12).
   For it is all for your sake, so that as grace extends to more and more people it may increase thanksgiving, to the glory of God (2 Corinthians 4:15).

Paul had strong faith in the resurrection of Jesus.
So we do not lose heart. Though our outer nature is wasting away, our inner nature is being renewed every day (2 Corinthians 4:16).
This hope of resurrection renews his inner nature so that Paul was able to go through all his sufferings. This is something which the Old Covenant cannot offer.

Dear Lord, very often we forget this hope in resurrection and fall into despair. May Your glorious resurrection give us strength to go through our daily frustrations. Amen. 

Appendix:
I believed, and so I spoke
ἐπίστευσα, διὸ ἐλάλησα (2 Corinthians 4:13, Psalm 115:1 LXX, 116:10 MT)