Bhagavad Gita 6.36
असंयतात्मना योगो दुष्प्राप इति मे मतिः।
वश्यात्मना तु यतता शक्योऽवाप्तुमुपायतः।।6.36।।
Asanyatatmana yogo dushprapa iti me matih
Vashyatmana tu yatata shakyovaptumupayatah
Simple meaning, written by AIMy view is that yoga is hard to attain for one whose self is not controlled. But for one whose self is controlled and who strives, it can be attained through the right means.