Cooperation between God and man “takes place when we make use of created things” according to Luther in Gustaf Wingren’s Luther on Vocation. And the way in which this cooperation takes place is through prayer.
Specifically, once our strength runs out, we must pray: “When work does not avail, when one’s strength no longer suffices, the time for prayer has come.” “[N]ot to turn to God in prayer for help in vocation, when all outward available possibilities are exhausted, is to blaspheme God and treat his promises as lies.”
But then, Luther — characteristically as I am beginning to find out — nearly goes overboard: “He who turns to God in prayer for help from above, without doing all he can with the help of the outward gifts God has given, is putting God to the test and cannot expect his prayer to be heard.” “Turning to God in prayer for help, without using the external means which God has given, is tempting God.”
This latter point is appropriate for someone lazy who sets up a false antithesis between prayer and work, and acting as though working rather than praying always implies lack of faith in God. Yet Luther’s statements come so close to suggesting that, if you get the sequence wrong — i.e., if you pray before you are absolutely sure you’ve done everything you could possibly do — you are testing God.
Yet the main point is worth noting: we get to cooperate with God in our vocation through prayer. So, how about this? Pray while working.