Krishna is always within us, and consequently He knows everything about our purposes, and He gives us the opportunity to work as we decide. If we decide to enjoy this material world, Krishna gives us the intelligence to become a very shrewd businessman or a popular politician or a cunning man so that we can earn money and enjoy ourselves.
According to the standards of material life, many people are becoming great. They begin as very poor men and soon, by good fortune, become millionaires. We should not think that they are attaining such success by their own puny endeavors. Without intelligence, no one can improve, and that intelligence is given by Krishna. One person can sharply remember past activities by the grace of the Lord while others cannot. One is highly intelligent by the grace of the Lord, and one is a fool by the same control. One cannot do anything unless he is enlightened and empowered by the Lord.
In the Bhagavad-gita Krishna states that He is seated in everyone’s heart as the Supersoul and that by His will a man can remember or forget. Krishna supplies forgetfulness and remembrance according to the living entity’s desire. If we want to forget Krishna and enjoy the material world, He will give us the necessary intelligence so that we can forget Him for good. When one is very serious about getting out of this material entanglement, the Lord, from within, gives him the knowledge that he has to surrender unto Him. He is so kind to His devotees that He gives them instructions by which they may continue to progress. When they receive instructions from the all-perfect, there is no chance of their being misled. Then there is liberation.
Ref: Chapter 8c, Science of Self Realization authored by Srila Prabhupada (Founder – Acharya, ISKCON)