Srimad BhagavadGita

Here, the statement buddhināśāt praṇaśyati B.G 2.63 is being elaborated by Kṛṣṇa. One who does not place his mind on Bhagawān's divine auspicious form which is the most auspicious refuge, cannot obtain a vision of the soul due to anyonyāśraya doṣa and as a result he is deprived of attaining the highest object of human pursuit, namely 'mokṣa'. How this happens is explained in this śloka.

Kṛṣṇa says, "One whose mind has no inclination towards ME does not understand the knowledge about the soul completely. One without this knowledge cannot contemplate on the soul. One who does not contemplate on the soul continues to crave for sense objects. Therefore he has no peace. How can one without this peace resulting due to relief from cravings, attain happiness?"

ayuktasya buddhir nāsti (One whose mind is not fixed on ME, does not understand the knowledge about the soul completely) Bhagawān who has a divine auspicious form which is the most auspicious refuge, can destroy one’s attachment towards sense objects even without soul realisation as a prerequisite for it and thus uplift the jīva from the anyonyāśraya doṣa. However, one who does not fix his mind on Bhagawān and strives to achieve sense control by his own efforts, can never succeed in spite of his great efforts. This is because control over senses cannot be achieved until the soul is realised, as told in B.G 2.59 raso’pyasya paraṃ dṛṣṭvā nivartate (his taste for sense objects does not exist anymore after he gets a vision of the essential nature of the soul) and soul realisation cannot be achieved until the senses are in control as told in B.G 2.61 yukta āsīta matparaḥ..., (when the mind and the other senses are in control, only then does he become firmly established in knowledge and achieve soul realisation as a result). So, no matter how much effort he puts in, he cannot realise the soul.

ayuktasya ca bhāvanā nāsti (One without this knowledge cannot contemplate on the soul) The pattern in the first three pādams (parts) of this śloka is such that, a pādam and its previous pādam have a word in common which links them just as joints hold the parts of a chain together. Going by this, the meaning of 'ayuktasya' in the second pādam is to be understood based on its meaning in the first pādam as 'abuddhiyuktasya'. In the first pādam, the result of being an ayukta is to become abuddhiyukta (lacking knowledge about the soul) and this is implied by the word 'ayuktasya' in the second pādam by lakṣaṇāvṛtti (taking the implied meaning to suit the context). Therefore the meaning is that, 'As told in the previous pādam, due to lack of complete understanding of soul knowledge, there is no desire to contemplate on the soul'. Alternatively, the meaning of 'ayuktasya' in the second pādam can be considered the same as that in the first pādam. The prose order will then be ayuktasya bhāvanā ca nā which means, 'For those whose minds have no inclination towards ME, realisation of the soul knowledge does not happen and as a result deep contemplation on the soul (ātma bhāvana) cannot happen.

abhāvayataḥ ca śāntir na In this way for a person who cannot do deep contemplation about the soul, his various attachments towards the sense objects are not in his control. Contemplation on the illustrious soul for a long time alone can lead to the destruction of cravings for meager sense objects. From the below Bhagawad Gītā ślokas raso’pyasya paraṃ dṛṣṭvā nivartate BG 2.59, rāga-dveṣa viyuktaiḥ BG 2.64, sukheṣu vigata spṛhaḥ BG 2.56, it is clear that removal of the cravings for sense objects is the topic of discussion in this chapter. Therefore, in line with the context, here the word śānti refers to the 'peace due to absence of craving for sense objects'.

aśāntasya kutaḥ sukham (How can one attain the highest happiness called mokṣa when his cravings for sense objects are not in his control?) Since people with attachment towards sense objects attain meagre rewards like heaven, etc, the word sukham here surely does not refer to heaven (the abode called swarga in this material world). It must be understood that it refers to the highest happiness called mokṣa. 

Summary:

Yama, niyama, āsana, prānāyāma, pratyāhāra, dhāranā, dhyāna, and samādhi are the eight limbs of aṣṭānga Yoga. For the four states starting from pratyāhāra, the following state is not achieved if the previous one is not achieved and thus mokṣa which is the final result of these states will also not be achieved. This is established by considering both the direct meaning and the implied meaning of the śloka.