As stated before, the Supreme Lord can be appreciated only by devotional service. Therefore, one should be fully devoted. One should fix his mind fully on Kṛṣṇa in order to achieve Him. One should work only for Kṛṣṇa. It does not matter in what kind of work one engages, but that work should be done only for Kṛṣṇa. That is the standard of devotional service. The devotee does not desire any achievement other than pleasing the Supreme Personality of Godhead. His life's mission is to please Kṛṣṇa, and he can sacrifice everything for Kṛṣṇa's satisfaction, just as Arjuna did in the Battle of Kurukṣetra. The process is very simple: one can devote himself in his occupation and engage at the same time in chanting Hare Kṛṣṇa, Hare Kṛṣṇa, Kṛṣṇa Kṛṣṇa, Hare Hare/ Hare Rāma, Hare Rāma, Rāma Rāma, Hare Hare. Such transcendental chanting attracts the devotee to the Personality of Godhead.
(Bhagavad-Gita---12:6-7---purport).

In the Seventh Canto of the Bhāgavatam, Sixth Chapter, verse 25, Mahārāja Prahlāda says, "My dear friends born into atheistic families, if you can please the Supreme Personality of Godhead, Kṛṣṇa, then there is nothing more rare in this world. In other words, if the Supreme Lord Kṛṣṇa is pleased with you, then any desire you may have within the core of your heart can be fulfilled without any doubt. As such, what is the use of elevating yourself by the results of fruitive activities, which are automatically achieved in all events by the modes of material nature? And what is the use for you of spiritual emancipation or liberation from material bondage? If you are always engaged in chanting the glories of the Supreme Lord and always relishing the nectar of the lotus feet of the Lord, then there is no necessity for any of these."
(Nectar of Devotion).

Any person who is always ready to satisfy Kṛṣṇa and who is always dexterous in executing devotional service is called dharma-vīra, or chivalrous in executing religious rituals. Only advanced devotees performing religious ritualistic performances can come to this stage of dharma-vīra. Dharma-vīras are produced after going through the authoritative scriptures, following moral principles, being faithful and tolerant and controlling the senses. Persons who execute religious rituals for the satisfaction of Kṛṣṇa are steady in devotional service, whereas persons who execute religious rituals without intending to please Kṛṣṇa are only called pious.
(Nectar of Devotion).

The performance of different yajñas for the demigods is considered to be worship of the limbs of the Supreme Lord. The demigods are considered to be different parts of the universal body of the Lord, and therefore the ultimate purpose in worshiping them is to please the Lord by partially worshiping His different limbs. Mahārāja Yudhiṣṭhira had no such material desire; he executed all sacrifices under the direction of Kṛṣṇa, and not to take any personal advantage from them. He desired only to please Kṛṣṇa and was therefore called the best of the devotees. He was always merged in the ocean of loving service.
(Nectar of Devotion).

An example may be given here to illuminate the above process of spiritualization. When the iron is put into the fire and becomes red hot, the iron then develops the qualities of fire and stops functioning as iron. In the same way, when all our activities are done in terms of our relationship with Kṛṣṇa, then everything is surcharged with spiritualization. Because pleasing Kṛṣṇa has become our ultimate goal, all our activities have become spiritual activities. In a sacrifice there are five primary elements—namely, (1) the process of offering, (2) the offering itself, (3) the fire, (4) the sacrifice, and (5) the result of the sacrifice. When all of these elements become related with the Supreme Spirit, all of them become spiritualized; and at that time the whole thing becomes really a sacrifice.
(Message of Godhead).