Bhagavad Gita Chapter 6, Verse 33

अर्जुन उवाच | योऽयं योगस्त्वया प्रोक्तः साम्येन मधुसूदन | एतस्याहं न पश्यामि चञ्चलत्वात्स्थितिं स्थिराम् ||

arjuna uvāca yo 'yaṁ yogas tvayā proktaḥ sāmyena madhusūdana etasya ahaṁ na paśyāmi cañcalatvāt sthitim sthirām

Arjuna said: O Madhusudana, this yoga that you have described by equanimity, I do not see how it can be maintained, because of the restlessness of the mind.

Arjuna expresses doubt about the practicality of yoga. 'Yo 'yaṁ yogas tvayā proktaḥ sāmyena'—this (ayam) yoga (yogaḥ) that you (tvayā) have described (proktaḥ) by equanimity (sāmyena). This means: Arjuna is referring to the yoga of equanimity, the balanced state, that Krishna has been describing. 'Etasya ahaṁ na paśyāmi cañcalatvāt sthitim sthirām'—I (aham) do not see (na paśyāmi) how firm (sthirām) stability (sthitim) of this (etasya) can be maintained, because of (tvāt) restlessness (cañcalatvāt). This means: Arjuna is honest about his doubt—he doesn't see how this yoga can be maintained because the mind is restless. The mind is fickle, unstable, constantly moving—how can one maintain equanimity? This is a sincere question from someone who's trying to practice but finding it difficult. Arjuna isn't rejecting the teaching—he's expressing the practical challenge he faces.