Personal Experience is the Great Persuader
Is there any better way to convince us that fire is hot than by letting us put our fingers in the flame (Matthew 5: 29-30)? Personal experience with the truth is more persuasive than a plethora of words about it - even when the source of the words is God. So God lets us put our fingers into the flame. The flame is extremely persuasive about the hotness of the fire. So, too, life without God in the valley of tears is extremely persuasive about its sourness.