Patanjali Yoga Sutra — 2.2॥samādhi bhāvanārthaḥ kleśa tanūkaraṇārthaśca॥

समाधि भावनार्थः क्लेश तनूकरणार्थश्च ॥

The practice of kriyāyoga helps the sādhaka to weaken or fade out imminent obstacles (mentioned in next sūtra) and aids him as an auxiliary to reach samādhi.

We have looming obstacles as well as auxiliaries for any journey to be undertaken. Spiritual journey or yoga sādhana is not an exception and there are interwoven impediments. It has its own obstacles as well as auxiliaries. Here it is said kriyāyoga sādhana eradicates or weakens the impending obstacles inherent in yoga.

Though the word‘kriyāyoga’ is not used by Bhagavān in Bhagavad Gītā, message in the following three ślokas is nothing less than that is stated by Patañjali Maharṣi.

बुद्धया विशुद्धया युक्तो धृत्यात्मानं नियम्य च।

शब्दादीन्विषयांस्त्यक्त्वा रागद्वेषौ व्युदस्य च॥गीता १८.५१॥

विविक्तसेवी लघ्वाशी यतवाक्काय मानसः।

ध्यानयोगपरो नित्यं वैराग्यं समुपाश्रितः॥गीता १८.५२॥

अहङ्कारं बलं दर्पं कामं क्रोधं परिग्रहम्।

विमुच्य निर्ममः शान्तो ब्रह्मभूयाय कल्पते॥गीता १८.५३॥

buddhyā viśuddhayā yukto dhṛtyātmānaṃ niyamya ca।

śabdādīnviṣayāṃstyaktvā rāgadveṣau vyudasya ca॥Gītā 18.51॥

viviktasevī laghvāśī yatavākkāya mānasaḥ|

dhyānayogaparo nityaṃ vairāgyaṃ samupāśritaḥ॥Gītā 18.52॥

ahaṅkāraṃ balaṃ darpaṃ kāmaṃ krodhaṃ parigraham|

vimucya nirmamaḥ śānto brahmabhūyāya kalpate॥Gītā 18.53॥

Blessed with pious thoughts, established in a clean and solitary place, self-restrained in food, having body, speech and mind under one’s own control, following stead-fast renunciation, established in incessant meditation, subjected to serenity, having mastery over internal faculties and destroyed ariṣaḍvargas, having renounced ego, arrogance, lust, antagonism, possessiveness, abandoning sense of ownership, with a composed mind, sādhaka, is now fit to be eternally blissful in communion with Brahman.

Yoga sādhaka‘s goal of life is nothing less than the realization of Paramātma and he is not satisfied with anything less than that.