There is a sort of insanity which can be hard to distinguish between it and holiness .

There is a sort of insanity which can be hard to distinguish between it and holiness . The difference is that every area of value has an opposite area of value. So holiness which is all essence and no form [God the Creator], can easily decay into an opposite area of value. That is the Dark side.  So to come to holiness is rather a process that is not well defined. One one hand, you might say that keeping Torah plain and simple ought to prevent one from falling into the Dark Side  [Sitra Achra]. But in everyday life, that is clearly not what happens. People that get involved in the Torah often end up as great disappointments. They are hurt and destroyed by those they trusted, and in turn destroy the life of others. Religious devotion most often causes a great deterioration in simple human decency. 

[I think is better to have balance between faith and reason according to the basic approach of the Middle Ages. But what is reason nowadays? In the Middle Ages that was at first Plato., Plotinus and later Aristotle. But that approach is a bit different after Kant.]