SB 6.1.62

stambhayann ātmanātmānaṁ
 yāvat sattvaṁ yathā-śrutam
na śaśāka samādhātuṁ
 mano madana-vepitam
Word for word: 
stambhayan — trying to control; ātmanā — by the intelligence; ātmānam — the mind; yāvat sattvam — as far as possible for him; yathā-śrutam — by remembering the instruction (of celibacy, brahmacarya, not even to see a woman); na — not; śaśāka — was able; samādhātum — to restrain; manaḥ — the mind; madana-vepitam — agitated by Cupid or lusty desire.
Translation: 
As far as possible he patiently tried to remember the instructions of the śāstras not even to see a woman. With the help of this knowledge and his intellect, he tried to control his lusty desires, but because of the force of Cupid within his heart, he failed to control his mind.
Purport: 

Unless one is very strong in knowledge, patience and proper bodily, mental and intellectual behavior, controlling one’s lusty desires is extremely difficult. Thus after seeing a man embracing a young woman and practically doing everything required for sex life, even a fully qualified brāhmaṇa, as described above, could not control his lusty desires and restrain himself from pursuing them. Because of the force of materialistic life, to maintain self-control is extremely difficult unless one is specifically under the protection of the Supreme Personality of Godhead through devotional service.