Jung is describing something most people experience as a crisis of authenticity — the gap between who you are and what you do all day — but he is actually describing health, not its absence. The neurosis is not the gap; the neurosis is the collapse of it. When the persona ceases to be a costume you can step into and out of and becomes instead the only self available, something much older and stranger in you goes silent.

What he is pointing to is a specific capacity: the ability to act fully and then return. To play Caesar — completely, without irony, without half-performing your own detachment — and then, when the scene ends, to become nothing in particular. Not nothing as defeat, but nothing as the ground that was always there beneath the role. The mask works when the face underneath it knows it is wearing one.

The danger is not the small tasks or even the performance. It is the forgetting — the moment the persona stops being provisional and starts being mandatory. That is when the soul's other contents, everything that does not fit the ready-made function, begin pressing from below in the forms that bring people eventually to analysis: symptoms, eruptions, dreams that insist on a life the ego never agreed to.