asaṃyatātmanā yogo duṣprāpa iti me matiḥ |vaśyātmanā tu yatatā śakyo'vāptumupāyataḥ ||
Yoga is hard to attain for one whose self is unrestrained — that is my view. But one whose self is under control, who keeps striving, can reach it by the right means.
Explanation
Krishna is replying to Arjuna's worry that the mind is too restless to master. He gives his considered view: yoga (disciplined union of the self with the highest reality) is very hard without self-restraint (saṃyama), but it is within reach for someone who has mastered the mind and keeps making effort. The "right means" (upāya) points back to the previous verse: steady practice (abhyāsa) and detachment (vairāgya).