What is the reason for the aversion to religious books and everything related to the science of the heart, and what is the fear of that, especially if there is rectification for the heart in them?

The science of purifying souls is one of the most noble sciences. There are several potential obstacles to seeking it, among them heedlessness of the Hereafter. The remedy for this is vigilance, attentiveness, preparing a sound heart, and persistent supplication. Another potential obstacle is fear of what is decreed, in the manner of some Sufis; the remedy for this lies in the books of the People of Sunnah. Yet another is the fear of not acting upon knowledge, which is an incorrect approach, for learning the science of the heart is obligatory, and you must seek Allah's help to act upon it. One should strive in supplication for the rectification of the heart and to abandon intrusive thoughts.