Why should a repentant servant combine hope and fear, even though Allah Almighty accepts sincere repentance?

Allah accepts the repentance of whoever is sincere in it, but it is not possible to definitively confirm the acceptance of a specific person's repentance due to the inability to verify the fulfillment of its conditions. Therefore, the servant remains between fear and hope, and these two are like two wings to a bird: hope dispels despair, and fear prevents complacency.