Iyās (despair) means giving up hope in Allah's mercy and forgiveness. It is mistaken to conclude after sinning that there is no longer any prospect of forgiveness.
Even numerous sins should not make a person despair of the mercy of their Lord. Hope in forgiveness remains, and the servant may still turn to Allah in need and remorse.
Both hope in mercy and fear of punishment retain their rightful place: neither false security nor despair is sound.