Anyone who takes to this chanting process will become saintly. He will become a pure, Kṛṣṇa conscious person.

So chanting Hare Kṛṣṇa will actually deliver all fallen souls, without doubt. This is not bogus propaganda. Whatever his past life, anyone who takes to this chanting process will become saintly. He will become a pure, Kṛṣṇa conscious person.

Chanting Hare Kṛṣṇa will purify our heart, our burning heart. Then we will understand, “I am an eternal servant of the Supreme Lord, Kṛṣṇa.” Ordinarily we can come to this understanding only after many, many births, as Kṛṣṇa confirms in the Bhagavad-gītā [7.19]. Bahūnāṁ janmanām ante jñānavān māṁ prapadyate: “After many, many births, when a person becomes a man of wisdom, he surrenders unto Me.” Why? Vāsudevaḥ sarvam iti: [Bg. 7.19] Because he knows that Vāsudeva, Kṛṣṇa, is everything. But that kind of great soul is very rare (sa mahātmā su-durlabhaḥ).

But Lord Caitanya has made it easy to become such a great soul. How? Simply by chanting Hare Kṛṣṇa. Therefore at the end of his song Narottama dāsa Ṭhākura says, hā hā prabhu nanda-suta vṛṣabhānu-sutā-juta koruṇā karoho ei-bāro: “My dear Lord Kṛṣṇa, You are now present before me with Your internal potency, Your pleasure potency, Rādhārāṇī. Please be merciful to me. Don’t neglect me because I am so sinful. My past life is so black, but don’t neglect me. Please accept me. Don’t kick me away. I surrender unto You.”

So, all of us should follow in the footsteps of Narottama dāsa Ṭhākura. The purificatory process is chanting Hare Kṛṣṇa. And as soon as our heart is purified, we will become completely convinced that Kṛṣṇa is the Supreme Lord and that we are His eternal servants. We have forgotten this. We are serving, but instead of serving the Lord we are serving our senses. We have never become the master. We are not the masters of our senses; we are the servants of our senses. That is our position.

So why not become the servant of the Supreme Lord instead of remaining the servant of your senses? Actually, you can become the master of your senses only when you become the servant of Kṛṣṇa. Otherwise, it is not possible. Either godāsa or gosvāmī: that is your choice. A person who is the servant of his senses is called godāsa, and a person who is the master of his senses is called gosvāmī. He controls his senses. When his tongue wants to eat something that is not offered to Kṛṣṇa, he thinks, “O tongue, you cannot taste this thing. It is not kṛṣṇa-prasādam [food offered to Kṛṣṇa].” In this way one becomes a gosvāmī, a master of his senses.

When a person does not allow his senses to do anything for sense gratification but acts only for the service of Kṛṣṇa, that is called devotional service. Hṛṣīkeṇa hṛṣīkeśa-sevanaṁ bhaktir ucyate: [Cc. Madhya 19.170] Devotional service means to engage your senses in satisfying the master of the senses. The supreme master of the senses is Kṛṣṇa. Now we are trying to use our senses for our personal service. This is called māyā, illusion. But when we engage the same senses in the service of Kṛṣṇa, that is perfection. We don’t stop the activities of the senses, but we purify the senses by engaging them in the service of the Lord. This is Kṛṣṇa consciousness.

Source : https://prabhupadabooks.com/jsd/3/liberation_to_a_higher_pleasure?d=1&f=257489