And the scariest part is that if you ask anyone in the throes of depression how he got there, to pin down the turning pont, he'll never know. There is a classic moment in The Sun Also Rises when someone asks Mike Campbell how he went bankrupt, and all he can say in response is, "Gradually and then suddenly." When someone asks how I lost my mind, that is all I can say too.

Do you not think that there are things you cannot understand, and yet which are; that some people see things that others cannot?...Ah, it is the fault of our science that it wants to explain all; and if it explain not, then it says nothing to explain.