In plain words
For one whose self is uncontrolled, yoga is difficult to attain—this is My view. But one who has mastered oneself and strives by the proper means can attain it.
Word for word
By one whose mind is unrestrained yoga is hard to attain: thus [is] My view; but by one whose mind is controlled, striving, [it is] possible to attain by the means.
असंयतात्मना योगो दुष्प्राप इति मे मतिःवश्यात्मना तु यतता शक्योऽवाप्तुमुपायतः
Other commentaries
The commentators
▸Bhagavadgītābhāṣyam
यः पुनः असंयतात्मा, तेन —
असंयतात्मना अभ्यासवैराग्याभ्यामसंयतः आत्मा अन्तःकरणं यस्य सोऽयम् असंयतात्मा तेन असंयतात्मना योगो दुष्प्रापः दुःखेन प्राप्यत इति मे मतिः । यस्तु पुनः वश्यात्मा अभ्यासवैराग्याभ्यां वश्यत्वमापादितः आत्मा मनः यस्य सोऽयं वश्यात्मा तेन वश्यात्मना तु यतता भूयोऽपि प्रयत्नं कुर्वता शक्यः अवाप्तुं योगः उपायतः यथोक्तादुपायात् ॥ ३६ ॥
In plain words
But someone whose mind isn't restrained—well, for him —
‘By one of unrestrained mind’—someone whose mind, his inner faculty, hasn't been reined in through practice and vairāgya—that is ‘one of unrestrained mind’; for such a person, yoga is hard to attain, gained only with great difficulty—that's my view. But whoever has a controlled mind—whose mind has actually been brought under control through practice and vairāgya—for him, striving further, making continued effort, yoga can be attained, through the means already described.
Close to the Sanskrit
Whoever, on the other hand, is of unrestrained mind—as for him —
‘By one of unrestrained mind’—unrestrained by practice and vairāgya, his mind, i.e. inner organ, of whom is so, he is ‘of unrestrained mind’; by that one of unrestrained mind, yoga is ‘hard to attain,’ i.e. is attained with difficulty—this is my opinion. Whoever, on the other hand, is ‘of controlled mind’—his mind, whose state of being controlled has been brought about by practice and vairāgya, of whom is so, he is ‘of controlled mind’; but by that one of controlled mind, striving, making effort still further, yoga is possible to attain, by the means, i.e. by the means as already stated.