Devotional advancement essentially means letting Krishna enter and rule our heart. This may happen in the following three progressive stages:

1. Permeation: Just as water from the clouds permeates into a field through the top soil, Krishna through his manifestations like the holy names, Deities and scriptures permeates into our heart through our senses. Just as the field primarily contains earth but allows water to penetrate, our heart at this stage primarily contains other attachments but allows Krishna to penetrate. We can equate this stage with the Bhagavad-gita (09.27) where the devotees offer whatever they do to Krishna. The erudite Gita commentator Vishvanatha Chakravarti Thakura underscores that as prescribed action precedes the devotional offering at this level, it is not an advanced level.

2. Pervasion: By gradual permeation Krishna spreads his presence all over our heart till he becomes the primary consideration and the prescribed duty, secondary. We can correlate this stage with the Bhagavad-gita (08.05) where the devotees offer their mind and intelligence to Krishna, indicating thereby his pervasion of their being. Naturally, therefore, they first remember him and then perform their prescribed duty. As Krishna comes first in the devotees’ thought-process, Vishvanatha Chakravarti Thakura deems this level higher.  

3. Possession: At this summit stage, Krishna becomes the devotees’ be-all and end-all. They care only for him and do whatever he instructs, irrespective of whether it harmonizes with their prescribed duties or not. The Gita (18.73) culminates with this level of devotion: karisyhe vacanam tava “I will do your will.” Herein, devotees don’t just gracefully submit to the will of God, as in the famous “Let thy will be done,” but go further and dynamically become instruments for executing that will.

Bhagavad Gita Chapter 09 Text 27

“Whatever you do, whatever you eat, whatever you offer or give away, and whatever austerities you perform do that, O son of Kunti, as an offering to Me.”