Lord Kṛṣṇa told King Yudhiṣṭhira that He is conquered by the love of one who has conquered his senses. One who has not conquered his senses cannot conquer the Supreme Personality of Godhead. This is the secret of devotional service. To conquer the senses means to engage them constantly in the service of the Lord. The specific qualification of all the Pāṇḍava brothers was that they always engaged their senses in the Lord's service. One who thus engages his senses becomes purified, and with purified senses the devotee can actually render transcendental loving service to the Lord and conquer Him.