"We can do nothing but by a supernatural grace of God. It is God who gives the will. It is God who gives the power." -- Calvin.
This is not only true before conversion, but also true of every facet of the Christian life after conversion. This is not only true for matters of "earthly providence and labor" but also especially true of every spiritual matter. (witnessing, preaching, loving, walking by faith, serving, laboring, praying, reading, and all)