The Catechism of the Catholic Church says that the first movement of the prayer of petition is asking forgiveness, like the tax collector in the parable. It is a prerequisite for righteous and pure prayer. A trusting humility brings us back into the light of communion between the Father and his Son Jesus Christ and with one another, so that 'we receive from him whatever we ask' (1John 3:22). The Catechism also states: 'To the extent that we are humble and faithful, we discover in meditation the movements that stir and heart and we are able to discern them.'
Obviously humility and prayer go together, and 'the humble' along with the poor, downtrodden, widows and orphans, are especially and particularly loved by God. We do not read of such love for the millionaire or company director, in fact they reeive a caution that for the rich it is difficult to enter heaven. They, or we, should not lose hope though, for what we do with what we have is what counts, and God, who sees everything we do, knows our actions, our intentions and our love, will judge us accordingly.
Paul, despite having every reason to do so, because of his past actions, does not doubt that the 'crown of righteousness' is awaiting him. He, having come to know Jesus, was humble enough to acknowledge his faults and change. He kept the faith.