(Sri Sri Radha Vrindavan Chandra)
"Every embodied soul is in the constant act of thinking. To refrain from thinking something is not possible for a moment. The duty of the individual, therefore, is to think of Kṛṣṇa. There should be no difficulty in this, nor any harm; Kṛṣṇa has pastimes and activities, He comes to earth and leaves His message in the form of Bhagavad-gītā, and there are so many literatures about Kṛṣṇa that thinking of Him is neither a difficult nor costly task. There are enough literatures on Kṛṣṇa to last one a lifetime, so there is no shortage of material. Thinking of Kṛṣṇa, however, should be favorable. If a man is employed, he may always be thinking of his employer: 'I must get there on time. If he sees me late, he may deduct from my paycheck.' This kind of thinking will not do. It is necessary to think of Kṛṣṇa with love (bhava mad-bhaktaḥ). In the material world when the servant thinks of the master, there is no love; he is thinking only of pounds, shillings and pence. Because that kind of thinking will not save us, Kṛṣṇa requests that one just be His devotee.
Thinking of Kṛṣṇa with love, or devotion to Kṛṣṇa, actually means service. The spiritual master prescribes various duties to enable the neophyte devotee to think of Kṛṣṇa. In the Society for Krishna Consciousness, for instance, there are so many duties assigned: printing, writing, typing, dispatching, cooking, and so on. In so many ways the students are thinking of Kṛṣṇa because they are engaged in the service of Kṛṣṇa.
What is the duty indicated by Kṛṣṇa? Mad-yājī māṁ namaskuru. Even if we are not inclined to obedience, we must obey and offer respects (namaskuru). Bhakti, or devotion, minus respect is not bhakti. One should engage in Kṛṣṇa consciousness with love and respect and should thus fulfill his designated duties. Then life will be successful. One can never be happy by identifying himself with the material body and engaging in all kinds of nonsensical activities. For happiness, there must be consciousness of Kṛṣṇa; that is the difference between spiritualism and materialism. The same typewriter, dictation machine, tape recorder, mimeograph machine, paper, ink, the same hand—on the surface, everything is the same, but everything becomes spiritualized when it is used in the service of Kṛṣṇa. This, then, is spiritual. We should not think that something has to be uncommon to be spiritual. The entire material world can be transformed into spirit if we simply become Kṛṣṇa conscious. By ardently following the instructions of Kṛṣṇa in Bhagavad-gītā and following in the footsteps of the great ācāryas, teachers of Bhagavad-gītā in the line of disciplic succession, we can spiritualize the earth and restore its inhabitants to sanity."
(Srila Prabhupada's Who Is Crazy?, Back to Godhead magazine #66)