Material sense gratification, sinful activity kills the propensity to serve Krishna.
When Nityananda accepts us as His, then there is no more sense gratification.
Materialistic sense gratification is simply filling of the holes (Knowledge acquiring senses). The more we fill the more they become empty & hungrier. The only way these holes can be filled is when we fill them with the Complete Whole.
Scientists are conducting research to find out how we can satisfy our senses more and more elaborately.
In this Kali-yuga, the demoniac mentality is employed in manufacturing various goods to facilitate the process of sense grantification.
A devotee doing sense gratification out of material conditionings, if keeps on listening to pure devotees, soon becomes disgusted of sense gratification and gives it up, and so attains the pure devotion to krishna.