असंयतात्मना योगो दुष्प्राप इति मे मतिः। वश्यात्मना तु यतता शक्योऽवाप्तुमुपायतः ॥

asaṅyatātmanā yogo duṣhprāpa iti me matiḥ vaśhyātmanā tu yatatā śhakyo ’vāptum upāyataḥ

Yoga is hard to attain, methinks, by a self that is uncontrolled; but by the Self -controlled it is attainable by properly directed energy.

In plain words: Krishna says yoga is very hard for someone with no self-control. But a person who disciplines himself can reach it by putting his effort in the right direction.