Foundation 86 from Zarrooq’s Qawaa`id at-Tasawwuf:
The perfection of worship is attained by guarding it and by carrying it out assiduously, which is in turn actualized by establishing both its outward and inward boundaries without either going to extremes or being remiss.
The lax performer of it is one who is wasteful of his lifetime, whereas the one who engages in it excessively has introduced an innovation in the Dīn, particularly in those instances where he believes that he draws closer to Allah by practicing worship more than the Dīn requires.
Due to the foregoing, people have said, ‘Whispering (al-waswasah) is an innovation (bid`ah), the original root of which consists in being ignorant of the Sunnah, coupled with a state of mental disorder which is driven away by persistent engagement in remembering Him through the following formula of dhikr, ‘Glory to the King, the Creator of everything (Subhāna’l-Maliki’l-Khallāq)’: «If He wills, He can dispense with you and bring about a new creation» (Sūrah Fātir: 16-7). The person affected by whispering recites that formula, constantly, whenever he is reading his habitual devotional litany (wird), and complements that by frequently practicing forms of recreation (deflecting his mind away from those whispered thoughts) and by acting in accordance with concessionary laws (rukhas) of the sharī`ah which have been advocated by people of knowledge as means of banishing such whispering. That is different from scrambling around for concessionary laws in the various juristic schools across the board of human situations, for that is mere perdition and straying into error, so understand.