Answer
It is beneficial to understand that sincere chanting makes us more receptive to the guidance of Paramātmā.
When one chants attentively, the influence of tamo-guṇa gradually diminishes. Under the influence of ignorance, a person becomes fixed in one way of thinking and is unwilling to change. As one advances toward sattva-guṇa, one becomes more receptive to higher guidance and more willing to abandon old patterns of thinking.
Unless a person is detached from previous habits, even if Paramātmā inspires him from within, he may not be willing to follow that guidance. Good chanting gradually creates the internal purity needed to receive such inspiration.
This is not a one-day process. One must chant attentively every day. As we continue this practice, Paramātmā invisibly guides us throughout the day, gradually changing our destiny.
We cannot determine how much of our intelligence is coming from past karma and how much is being inspired directly by Kṛṣṇa. Ultimately, all actions are based on intelligence, and it is impossible to separate these influences precisely.
However, one thing is certain: if a person does not chant at all, then whatever intelligence he displays is simply the result of past karma.
Someone may perform a service more efficiently than another devotee who chants sixteen rounds, simply because of different karmic impressions. Therefore, external success alone is not a reliable measure of spiritual advancement.
Kṛṣṇa is the sanctioner, witness, and guide. We should therefore avoid judging another person's purity based on visible results.
Similarly, we should not constantly measure our own purity by the outcomes of our service. Instead, we should honestly evaluate whether:
I performed my sādhana properly.
I followed the instructions of Śrīla Prabhupāda.
I fulfilled my duty sincerely.
Purity should be evaluated by faithfulness to the process, not by external success.
If we begin linking every result to our perceived level of purity, we may draw incorrect conclusions. This can lead either to unnecessary discouragement when results are poor or to false pride when results are favorable.
The proper focus is simply to perform one's devotional practices sincerely, execute one's prescribed duties faithfully, and leave the results to Kṛṣṇa.