「that, as it is written, "He who glories, let him glory in the Lord."」 Amen.
You don't have to mourn the lack of faith. You don't have to think that you are contributing nothing as a Christian. We do not have faith, so we rely on the Lord. We feel helpless, so we should come under Jesus on the cross and pray. The more you lament that you have nothing to be proud of, the sooner you are proud of the Lord. This is his grace.