Amn (false security) is the mistaken sense of safety in which a person has no fear of Allah's punishment, whatever their deeds may be.
To suppose that every sin must be forgiven and that no accountability is possible is not balanced belief. A person cannot treat their deeds as being beyond Allah's judgment.
Fear of Allah guards against heedlessness and unwarranted assurance. Hope in mercy must not be turned into a denial of punishment and accountability.