"This body is the encagement of our nescience, of our ignorance. And in that body the senses are our greatest enemies. Out of that, the tongue is the most powerful enemy." Tā'ra madhye jihwā ati lobhamoy sudurmati. Lobhamoy sudurmati. Because tongue is always hankering after palatable things, and it is making me bound up in so many reactions of my life. That is the secret.
Therefore, in the Bhagavad-gītā, in the beginning, the karma-yoga begins with the tongue. Yajña-śiṣṭāśinaḥ santaḥ. We have to eat. Now, we have to control the tongue first. How we can control the tongue? By offering sacrifice. By offering, we have to take foodstuff for maintaining our body. Now, if we offer the foodstuff, preparing to the Lord, that is called yajña.
Yajña is not very difficult thing. You are preparing foodstuff for eating at your home. You have simply to prepare that foodstuff in a nice way, so that you can offer to Kṛṣṇa. That's all. Your process of eating or your process of securing ingredients for eating, or your cooking, nothing is stopped. Only, only thing is required that instead of cooking for yourself for the satisfaction of your tongue, you please cook it for satisfaction of Kṛṣṇa and take the prasādam afterwards.