The best thing we can do is eat and drink and enjoy what we have earned. And yet, I realized that even this comes from God. 1
How else could you have anything to eat or enjoy yourself at all?
God gives wisdom, knowledge, and happiness to those who please him, but he makes sinners work, earning and saving, so that what they get can be given to those who please him. It is all useless. It is like chasing the wind. 2