maccittaḥ sarvadurgāṇi matprasādāt tariṣyasi । atha cet tvamahaṅkārānna śroṣyasi vinaṅkṣyasi ॥ 18-58॥
Being one whose mind is always in Me, you will cross all difficulties because of my grace. If, because of egotism, you do not listen (to Me), you will perish.
Durga means that which is difficult to cross. A mountain peak or a narrow passage, which is difficult to negotiate, is called durga. It is something that can be crossed only with great difficulty. It is karma which is the cause of samsāra, which creates punya-pāpa that causes new births. They are born of a sense of agency - kartrtvam, which itself is born of ignorance, all of which are very difficult to cross. But, being one who is committed to a life of karma-yoga, one will cross all difficulties which are difficult to cross - sarvadurgāṇi tariṣyasi.
Lord Krsna says, suppose you don’t listen to me - atha cet na śroṣyasi, because of your own egotism - ahaṅkārāt, because you think you know everything and are going to take charge of everything. If that is the case, you will get destroyed - vinaṅkṣyasi, meaning you cannot accomplish what you want. Moksa that you are seeking will be denied to you because you are not ready for it. If you are not ready for sannyāsa and you give up karma, you will neither be a sannyāsī nor a karma-yogī. Therefore the word destroy is in the sense that you will not get that end which you are seeking. Lord Krsna says this only to make sure that Arjuna has understood him properly because later he is going to give him the freedom to choose whatever he wants.
Lord Krsna wants to make sure that he has said everything he has to say. He is telling Arjuna that even though the duty he has to do here is not pleasant, if he gives it up, he will have to do something more unpleasant later, because his rajasika nature as a ksatriya has to grow become sāttvika nature only if he has done his duty. Arjuna’s disposition at that time was something that had to be taken care of for the purpose of moksa. Therefore Lord Krsna continues…
yadahaṅkāramāśritya na yotsya iti manyase । mithyaiṣa vyavasāyaste prakṛtistvāṁ niyokṣyati ॥ 18-59॥
Resorting to egotism, you think, “I will not fight.” This resolve of yours is false. Your disposition will impel you.
Arjuna may go away from the battlefield and take the life of sannyāsī, but that will be problematic for him later. Because prakṛtistvāṁ niyokṣyati - your nature will bind you. He has not grown into the disposition of a brāhmana. He is a fighter by nature and this will force him to do the action of a ksatriya. Lord Krsna explains further, in the next śloka.
svabhāvajena kaunteya nibaddhaḥ svena karmaṇā । kartuṁ necchasi yanmohāt kariṣyasyavaśo'pi tat ॥ 18-60॥
Kaunteya (Arjuna)! Out of delusion, being definitely bound by your own action, which is born of your natural disposition, you will helplessly do just what you do not wish to do.
svabhāvajena - born out of one’s disposition, determined by the composition of the three guna, sattva, rajas, and tamas. By guna, one is definitely bound - nibaddhaḥ, to perform certain action, even what you do not want to do - yat kartuṁ necchasi. Why? mohāt - because of delusion, he acts with the lack of discrimination. kariṣyasyavaśo'pi tat - helplessly do just what he doesn’t wish to do. When the pressure goes away, he will regret his failure to act. Being completely possessed by a given disposition, one will act in accordance with it.
There is no escape from it, because one cannot change his disposition overnight. One has to go through his duty and change the disposition through that duty alone.
As a karma-yogī, one has a field to change one’s disposition into sāttvika disposition, which is necessary for knowledge that is free from obstructions. Whereas this field is not available for sannyāsī who has renounced all his duties. To remove all the obstructions, one has to go through a life of duty keeping Īśvara in view.
Now Lord Krsna comes back to the main teaching.
īśvaraḥ sarvabhūtānāṁ hṛddeśe'rjuna tiṣṭhati । bhrāmayan sarvabhūtāni yantrārūḍhāni māyayā ॥ 18-61॥
The Lord remains at the seat of the intellect of all beings, Arjuna! Causing all beings to move (revolve), by (the magic of his) māyā, (like) those (figures) which are mounted on a machine (are made to revolve).
Īśvara is the one in whose presence, the mind, senses, etc., function as they do and the whole universe is as it is. That Īśvara is said to reside at the seat of the intellect - hṛddeśe, because that is where consciousness is manifest, where we experience the whole world and where we recognise the presence of ātmā - self. There alone I recognise “I am”, and same for all beings - sarvabhūtānāṁ. Residing there, Īśvara is causing all being to revolve - bhrāmayan sarvabhūtāni, because of his presence alone, without any involvement at all on his part, the mind and others organs are doing their job. Everything is moving because of ātmā that is behind, without which there is no being for anything. Giving existence and also consciousness of the mind, sense, etc., it remains hidden.
A very interesting example is given here. The beings are made to move by Īśvara, like the figures mounted on a machine are made to revolve as if by magic - bhrāmayan sarvabhūtāni yantrārūḍhāni māyayā (iva). Just like a merry-go-round, we only see varieties of dolls revolving without seeing the machine which makes the turning happen, which appears like magic - māyāya.
Just as the magician who runs this show stands there without being seen, Īśvara remains in the intellect of all beings, making them move, as the law of karma. Accordingly, each person is going to function in keeping with his disposition. How are we going to change that unless we deliberately initiate the process of change?