Self, or the phenomenon of ipseity, constitutes our consciousness, such that consciousness is in fact understood and experienced as self-consciousness. (Mysticism has a more expansive understanding of consciousness, however, which transcends the determination of historical time.)
It is commonly understood that when one’s experience of self is seriously problematised, mental illness occurs.
This is based on a non-mystical understanding of self, not only by society but by the mental health consumers or patients themselves.
The overall construct of mental illness is based upon an exoteric, not esoteric, interpretation and understanding of consciousness. (Esotericism is built on mystical insights.) This construct is a form of hermeneutics stalled in the phenomenon of what Heidegger calls the “everyday”, which determines a form of Dasein known as das Man – the everyday people.
Mental illness is a profound experience of coming up against a wall built unquestioningly by the everyday people in their everyday activity.
In one aspect, the occurrence of mental illness signifies the oppressive power of das Man in how ipseity is to be experienced and understood. Hence the abyss which opens up in normality, feared and rejected by society as “madness”, actually provides an opening for a deeper experience and understanding of ipseity.
When there is clarity in ipseity, mental illness disappears.
Blaue Hermeneutik 
I appreciate your thoughts and comments, Blaue (if I may refer to you informally. But the ontic life is necessary for being-in-the-world. I would agree that mental health is built solely on an exoteric rather than an esoteric view. But I find it necessary to be so, especially in cases of more severe mental illness. Otherwise one slips into the mire of another’s abyss. No one is helped in that scenario (where the goal of help is to survive and stay alive in this world). Ipseity cannot be found in the abyss. But it is helpful to know that it is there for each of us. Faith is another way to anchor one’s selfhood, which sets a post in the mire of the abyss. Even so, one must go about ones business (integrating apprehension of self, ones dasein) on the appearance of solid ontic ground, even though the abyss of the water table is not too far below. Clarity in ipseity, as an ideal, must give way to acceptance of being in the world as it is and where one finds oneself.