Perhaps an inheritance from primitive ancestors that grew to fear the coming winter frosts, as their very survival was threatened by it? With an affective disorder, which is basically an increasing emotional instability, it is almost as if the shielding obscuring the lower brain is lifted as it struggles to assert itself, bringing into full view an engine fashioned in ancient times, with all of the attendant quirks. And the executive's eyes grow into saucers as it becomes apparent it will have to manage an increasingly turbulent landscape of sinking despair with occasional eruptions of manic grandiosity and urgency.
In the course of a single day one can find oneself lost amongst surging currents of incredible grief, to be deposited on a distant shore shaken, yet alive, with the subsequent euphoria that comes with survival triggering another mad rush of thought and feeling. Exhausting, this life, but worthwhile.