Bhagwad Gita
Chapter 6, Verse 36
असंयतात्मना योगो दुष्प्राप इति मे मतिः।
वश्यात्मना तु यतता शक्योऽवाप्तुमुपायतः।।6.36।।
For one whose mind is unbridled, self-realization is difficult work. But he whose mind is controlled and who strives by right means is assured of success. That is My opinion.