Bhakti Sandarbha 209 : The bhajana-śikṣā guru is also necessary
शिक्षागुरोरप्यवश्यकत्वमाहुः (भा. १०.८७.३३)—
य इह यतन्ति यन्तुमतिलोलमुपायखिदः।
व्यसनशतान्विताः समवहाय गुरोश्चरणं
वणिज इवाज सन्त्यकृतकर्णधरा जलधौ॥
The śikṣā-guru is also necessary, as stated by the personified śrutis:
O birthless Bhagavān! The mind is like a wild, unbridled horse. Those who endeavor to control it through mastery over their senses and breath without taking shelter of the feet of a guru, cannot do so. They are troubled by the very methods they adopt and are beset with hundreds of tribulations in this world. They are like merchants who attempt to cross the ocean on a ship without a captain. (SB 10.87.33)
ये गुरोश्चरणं समवहाय अतिलोलमतिलोलुपमदान्तमदमितं मन एव तुरगं विजितैरिन्द्रियैः प्राणैश्च कृत्वा यन्तुं भगवदुन्मुखीकर्तुं प्रयतन्ते ते उपायखिदः, तेषु तेषु उपायेषु खिद्यन्ते। अतो व्यसनशतान्विता भवन्ति। अत एव इह संसारे तिष्ठन्त्येव।
Those who avoid the feet of the Guru and attempt to control the mind, which is like a wild, unbridled horse, i.e., to turn it towards Bhagavān through mastery of the senses and life airs, are tormented by the very methods they adopt. They thus meet with hundreds of obstacles and as a result certainly remain here in this material world.
हे अज ! अकृतकर्णधरा अस्वीकृतनाविका जलधौ यथा, तद्वत्।
O birthless one (aja) ! Such people are compared to merchants who try to cross the ocean on a boat without having engaged a navigator.
श्रीगुरुप्रदर्शितभगवद्भजनप्रकारेण भगवद्वर्त्मज्ञाने सति तत्कृपया व्यसनानभिभूतौ सत्यां शीघ्रमेव मनो निश्चलं भवतीति भावः।
The import is that when one becomes situated in wisdom related to the devotional path by engaging in the worship (bhajana) of Bhagavān under the instruction of one’s guru, then by the mercy of the guru one is no longer overwhelmed by obstacles and the mind very quickly becomes stable.
मिलितोऽपि न लभ्येत जीवैरहमिकापरैः॥
Therefore it is said in the Brahma Vaivarta Purāṇa:
By devotion to the guru one remembers Bhagavān; and by such remembrance one attains Him. Bhagavān is thus served by the wise. But those who are proud of their knowledge cannot attain Bhagavān, although He may be present before them.
श्रुतिश्च (श्वे.उ. ६.२३)—
तस्यैते कथिता ह्यर्थाः प्रकाशन्ते महात्मनः॥ इति॥
The śruti also says:
The meaning of the teachings described herein is revealed only to that great being who has supreme devotion unto Bhagavān and the same quality of devotion to his or her spiritual teacher. (Śvetāśvatara Upaniṣad 6.23)
Commentary by Satyanarayana Dasa Babaji Maharaja
As said earlier, the śikṣā-guru means the one who instructs the bhakti-yoga practitioner in the practical details of its practice. Although bhakti is a simple and natural process, one does need to learn it properly. There are always two ways of doing a thing, properly and improperly. That leads to two different results, i.e., proper and improper. If we want a proper result then it behooves us to act properly, and that means we need to learn from a genuine guru. We need to learn everything from others, even how to use the toilet. Bhagavān is not visible to us. How can we know by ourselves how to reach Him? Our minds are turbulent, as Arjuna says,
cañcalaṁ hi manaḥ kåñṇa pramāthi balavad dåḍham
tasyāhaṁ nigrahaṁ manye vāyor iva suduñkaram
tasyāhaṁ nigrahaṁ manye vāyor iva suduñkaram
O Kṛṣṇa, because the mind is very unsteady, turbulent, strong and rigid, I consider it extremely difficult to control, like the wind. (Gītā 6.34)
It is not possible to control it without proper guidance. Even the simple process of chanting mantra, japa, needs guidance. Otherwise people go on chanting for decades without much progress. One needs to be given the proper medicine and also know how to take it properly, at the proper time in the proper amount. Just as one cannot be one’s own doctor -- not even those who are themselves doctors -- so one cannot be one’s own guru. The spiritual subject matter is beyond sense perception, therefore it requires expert guidance. Millions of people take to spiritual life but the success rate is very low. The primary reason for this is lack of proper guidance.
Bhakti Sandarbha 208 : There is No Possibility of Knowledge Without Guru
Bhakti Sandarbha 207 : Dīkṣā Guru is Only One
Bhakti Sandarbha 206 : The śravaṇa- and bhajana-śikṣā-gurus are usually the same person
Bhakti Sandarbha 204-5: Proper Deliberation on Śāstra Brings About Śraddhā in Bhajana
Bhakti Sandarbha 203: The Guru Should not be Greedy
Bhakti Sandarbha 202 : The Necessity of Guru : Different Types of Sadhus Give Different Types of Bhakti
Bhakti Sandarbha 202: The two devotional proclivities and taking a Guru
Bhakti Sandarbha 201 : The Ananya Bhakta is Superior to the Jñānī Bhakta
Bhakti Sandarbha 200 : The Intermediate Devotee Renounces Karma