CC Madhya 13.138
vraja — āmāra sadana, tāhāṅ tomāra saṅgama,
nā pāile nā rahe jīvana
Only when the mind is free from designations can one desire the association of the Supreme Personality of Godhead. The mind must have some occupation. If a person is to be free of material things, his mind cannot be vacant; there must be subject matters for thinking, feeling and willing. Unless one’s mind is filled with thoughts of Kṛṣṇa, feelings for Kṛṣṇa and a desire to serve Kṛṣṇa, the mind will be filled with material activities. Those who have given up all material activities and have ceased thinking of them should always retain the ambition to think of Kṛṣṇa. Without Kṛṣṇa, one cannot live, just as a person cannot live without some enjoyment for his mind.