The following song is sung by Narottama dasa Thakura: ahankare matta hana, nitai-pada pasariya, asatyere satya kari mani Due to forgetting the lotus feet of Lord Nityananda and being puffed up by material possessions, wealth and opulence, one thinks the false, temporary material world to be an actual fact. This is the material disease. The living entity is eternal and blissful, but despite miserable material conditions, he thinks the material world to be real and factual due to his ignorance.
>>> Ref. VedaBase => SB 5.14.5