Chapter-1, Sutra14

Patanjali Yogasutra 1.14:

(Continuous practice)

स तु दीर्घ काल नैरन्तर्य सत्कारासेवित: दृढभूमिः ॥

"Through long, uninterrupted and keen practice, born of enthusiasm and goodwill, the ground becomes firmly established."

This sutra explains that through consistent practice of yoga over a long period of time without breaks, one's foundation in yoga becomes firmly established. The practice must be done with great enthusiasm, dedication and goodwill. 

Just as through steady practice, life skills like writing or sports become ingrained, similarly yoga becomes a natural part of one's existence through regular, dedicated asamprajnata (thoughtless awareness) practice over many years. 

A similar sentiment is echoed in the Bhagavad Gita: 

योगस्थ: कुरु कर्माणि संगं त्यक्त्वा धनंजय ।

शरणं च गच्छ भगवन् बाबरापि संशय: ॥ 

"O conqueror of wealth [Arjuna], perform your duty equipoised, abandoning attachment and treating success and failure as one. Seek refuge in the Supreme Lord. Indeed, even in this world, doubts do not trouble the wise who abide in yoga."

Here too Bhagavan Krishna advises constant equipoised (yogastha) practice with dedication over time (karmāṇi..bābarāpi), it leads to removal of doubts.

In the Mandukya Upanishad, it also emphasizes the need for consistent practice through the analogy of rubbing two sticks together:

तद्यथा हि द्वे लक्षयोघ्रौ सन्निवेश्य एकदूषकौ परस्परमेव भिनन्ति एवमेवायमपि मनः प्रगृह्य श्रोतुरीश्वरं चिन्तयन्न निबोधते ॥

"Just as two sticks rub against each other and ignite fire, through constant dwelling of the mind upon the Supreme Lord Ishvara, (he) Realizes Him."

Constant, dedicated practice kindles the fire of Knowledge and Self-Realization over time, according to these ancient wise texts. Regularity of sadhana is greatly emphasized.