Moses was unalterably, unequivocally, irrefutably called to this job to bring God's people out from Egypt. But the first attempts to do so resulted in complete and utter failure. On first attempt, in fact, things got worse. Pharaoh ordered that the Hebrews make the same amount of bricks, but with no straw provided; they must gather it for themselves. Israelite leaders are beaten for not making quotas.
The lesson? Initial failure in a task is no measure of calling. In fact, things may get worse. Immediate results are to be gauged appropriately, not ignored. But they are quite secondary. They are not definitive. They are largely irrelevant. What must Moses have been thinking by the end of Exodus 5?
The answer? Faith and patience. Christ is enough. The promises aren't going anywhere.
And we desire each one of you to show the same earnestness to have the full assurance of hope until the end, so that you may not be sluggish, but imitators of those who through faith and patience inherit the promises. (Heb 6:11-12)