Gradually you will understand what it means to please Krishna and what it means to displease Krishna. That you will learn by studying our books and by yourself engaging in practical devotional service. In the material dealings there is always there is always something undesirable, but even so you cannot give up your occupation. Just like fire is very pure, still there is some smoke. You cannot avoid it. All these things can be rectified when the result is offered to Krishna. Otherwise even though you may do very honest business it has no utility whatsoever.
Letter to Yajnesvara, 2 January, 1972