Nietzsche spoke about these moments of great self-contempt when you are above yourself, looking down, disgusted at yourself, shameful of this reject little ape you are.
This, I suppose, was a step towards self-overcoming — but it is not self-overcoming itself, of course. Not only do you have to hold that self-contempt but you must use it as an inspiration for action, to work towards making that self less contemptible, if nothing else.
What is it about this self-contempt that makes it such a launch pad? The self you see, the one which you are above and looking down upon, is clearly apart from you, so despite the fact that you’ve been parading around through your life playing that role, that isn’t you. The eye cannot see itself, but must rely on reflection — too often in the form of representation — or on a convincing lie to which it naively comes to identify. As you now recognize yourself as distinct from the contemptible imago, the object of your “self” contempt brings you to this self-realization. By process of elimination the self for whom you hold contempt is not you, so change things so that it becomes a masque more fitting for the face forced to bleed and receive through it.