I will whilst will not but will

My gifted silver necklace blessed by the heart with sanctuary promises I will fail you
My hero my imaginary friend I will fail you
My heart my source of demise I will fail you
My mother my bubble of imaginary eternal protection I will not fail you
My father my beloved and loathed king of injustice I will fail you
My lover my rock my source of inquiry war and adoration I will not fail you
My God my conscience from within and beyond I will not fail you

What is the difference between I will not fail you and I will fail you? There's only one: the former expresses intent to meet expectations and the latter lucidity.

I will fail YOU.