I had fainted, unless I had believed to see the goodness of the Lord in the land of the living. In the original, by the figure aposiopesis,, the apodosis is omitted, "had I not believed that I should see the goodness of Jehovah in the land of the living [i.
e. in this present world], then … " He shrinks from stating the consequences, He would have fainted, or despaired, or lost all faith in religion (compare, for similar uses of the figure aposiopesis, Genesis 3:22; Genesis 31:41; Genesis 50:15; Exodus 32:32; Daniel 3:15; Zechariah 6:15; Luke 13:9).
By an effort of faith, the psalmist saved himself from the despair which threatened to seize upon him, and assured himself that he would yet experience "the goodness of the Lord" in some merciful interposition and deliverance, while he still remained on earth, before he "went whence he should not return—to the land of darkness and the shadow of death, a land of darkness as darkness itself, and of the shadow of death, without any order, and where the light is as darkness" (Job 10:21, Job 10:22).