Should the devotee always speak the truth to everyone in all circumstances? The answer is yes, one should always speak the truth, but qualified devotee will be able to speak the truth always very palatable to everyone so that it will sound pleasing even to his enemy, that is the art of speaking truth. It is certainly so that we must speak the truth to all people, but how you say it that is another thing: satyam bruyat, priyam briya. When you become yourself little more experienced in Krishna Consciousness by preaching work and if you are sincere and serious to make progress in spiritual understanding, you need not have to worry yourself further because the truth will always be spoken by you in the proper manner. Krishna will give you that intelligence, you need not be concerned for it. Simply try to please Him always by your sincere service and chanting, that's all.
Letter to Yajnesvara, 2 January, 1972