Job had the blessing, but was working to keep it, as verse 5 of the first chapter shows us. He did not fully know grace, and was miserable, as he himself says in chapter 3:25, 26.
God sent all the trial to teach him grace so that he might know that he neither deserved the blessing, nor could he keep it.
This lesson, when learned, made Job a happy man. How many there are like Job! If I get the blessing without deserving it, it is clear I can never lose it for want of merit. We stand in grace (Rom. 5:22By whom also we have access by faith into this grace wherein we stand, and rejoice in hope of the glory of God. (Romans 5:2)). Working to keep the blessing—with that object—is to have fallen from grace (Gal. 5:44Christ is become of no effect unto you, whosoever of you are justified by the law; ye are fallen from grace. (Galatians 5:4)).