First of all, you have to act accordingly; then you can teach others. And if you are not pure, if you indulge in all kinds of sinful activities and you talk of Bhagavad-gītā, what will be effect? There will be no effect. This is going on.
They are doing all nonsense, and talking of Bhagavad-gītā. Therefore it is not effective. For last one thousand years Bhagavad-gītā was known in the Western countries, but there was not a single krsna-bhakta. Because they did not act accordingly. Simply talked of Bhagavad-gītā. That’s all. Simply talking will not do. You have to behave as these people are, these boys and girls are behaving. Then you will understand Bhagavad-gītā.
Srila Prabhupada, Lecture on Bhagavad-gita As It Is 7.1-3 in London, August 4th 1971
Grihastha Life 