Sree Sree Guru Gaurangau Jayatah!
In this Kali-yuga, if we try to remember Sri Krishna by meditation, which is prescribed for Satya-yuga, the golden age, we will not be able to remember. Our minds are very restless, dwelling on the non-eternal things of the world. Impressions of lakhs (100,000) and lakhs of births are stored in the mind. There are four kinds of piety: tapah, saucam, daya, and satyam (austerity, cleanliness, mercy and truthfulness). In Treta-yuga, when one of these four (tapah) had become diminished, it was not possible to practice meditation. Then sacrifice to Lord Vishnu was prescribed. If you have attachment for worldly things, you should give those worldly things for the service of Bhagavan Sri Krishna. In this way, you can concentrate on the ultimate target of worship. This could be accomplished in Satya-yuga by meditation, and in Treta-yuga by sacrifice.
In Dvapara-yuga, two kinds of piety had become diminished, tapah and saucam. People became more influenced by the senses and became incapable of uttering mantras correctly. Thus, they could not perform sacrifice. So the people of this era were told, “You should worship the Deity and engage all the senses and the objects of the senses in this way.” All indriyas, all gross and subtle senses, including the mind, should be engaged in the service of Sri Krishna. If you serve the Deity, you have dedicated all the sense organs and all the objects of the sense organs. The purpose of this is to develop concentration on the object of devotion.
But in Kali-yuga we cannot perform Deity worship because we are diseased. A diseased person is prohibited from Deity worship. We are incapable of rising early in the morning. We cannot sit in the temple for a long time. Two or three hours are required for worship. After half an hour, we become distracted. We are diseased, so how can we worship? There is one sloka:
krte yad dhyayato vishnu
tretayam yajato makhaih
kalau tad hari-kirtanat
(Srimad Bhagavatam, 12.3.52)
“Whatever benefit human beings received in Satya-yuga by meditation, in Treta-yuga by sacrifice and in Dvapara-yuga by Deity worship, they can receive in Kali-yuga by the chanting of the Holy Name.”
— Srila Bhakti Ballabh Tirtha Goswami Maharaj