Yoga Sutras 1-14: स तु दीर्घकालनैरन्तर्यसत्कारासेवितो दृढभूमिः

sa tu dîrgha-kâla-nairantarya-satkârâsevito dṛḍha-bhûmiḥ

When that practice is done for a long time, without a break, and with sincere devotion,

then the practice becomes a firmly rooted, stable and solid foundation.